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Posted by: Phil Stooke Jul 1 2005, 01:30 AM

Oh well, might as well start that new topic since it's already well advanced in the Juno area...

My perspective on landers is as follows. All the landers we've had so far were dropped blind onto an essentially unknown surface. Any future landers can be targeted for specific terrains. It really is not true that we have had representative landings. Even a descent image or two, a panoramic photo plus a bit of surface composition, from a simple Venera-class lander just updated a bit, would be useful if we could put several down at well chosen targets. My choices would be:

Examples of the main plains units (smooth, fractured, ridged)

tesserae

high elevation radar-bright tesserae

large fresh lava flow unit ('fluctus')

crater dark parabola

crater ejecta outflow unit

dunes area.

And I have always assumed, rightly or wrongly, that it would be relatively easy to put these down, so they ought to be fairly inexpensive as planetary landers go.

Phil

Posted by: BruceMoomaw Jul 1 2005, 09:23 AM

Well, to repeat a point I've suggested (somewhere) on this site before: given the great additional difficulty of designing a Venus probe if you have to add an airlock to it to allow it ingest samples into its interior, how much good compositional data can you get on Venus' surface WITHOUT such an airlock. A surprising amount, I suspect. A test has already shown that the LIBS system planned for instantaneous, precise and long-distance element measurements on the MSL rover should work just as well in Venus' environment ( ).

On Mars and on airless worlds, this instrument can probably be combined with a Raman spectrometer (which also uses laser light) for a lot of mineralogy studies (although this system wasn't considered quite ripe enough by the LIBS group right now to add it to their proposal for the MSL's LIBS; it's worked fine in ground tests). I'm not sure whether Raman would work as well at long-range in the super-dense Venusian atmosphere -- it relies on measuring an extremely small trace of backscattered laser light -- but even if it doesn't, you could put the fiber-optic connections to a Raman spectrometer and its laser on a simple arm on the lander to contact the local surface in different places. You could also add other gadgets to that arm: a microscopic imager, and maybe even an abrading wheel to grind the weathering crust off Venusian rocks -- which the lander could probably locate on the surface using a simple hardness sensor on the arm.)

Add a panning near-IR spectrometer to the lander (plus a tiltable flashlamp (or broadband laser) to periodically illuminate the surface and allow that spectrometer to distinguish its reflectance spectra from thermal emission spectra), and maybe also a gamma-ray spectrometer inside the lander's hull, and you could answer damn near every important scientific question about Venus' surface -- except for in-situ age dating -- without ANY airlock, and without any need for instruments that require a long time to gather their data (such as X-ray and Mossbauer spectrometers). An X-ray diffractometer like the one on MSL (which also requires ingested samples) could provide additional mineralogy data, but I question whether it's really essential by itself given the Raman and near-IR spectrometers.

Posted by: BruceMoomaw Jul 1 2005, 09:27 AM

I see I forgot to provide the URL for the LPSC abstract on the use of LIBS on Venus. *sigh*

http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1338.pdf

Posted by: JRehling Jul 1 2005, 04:28 PM

Phil is, of course, completely right about the list of interesting Venus terrains; I think anything but an aerobot approach will leave us a long time in seeing all of them, but a network of four geophysical stations ought to be chosen opportunistically to sample some of the more unusual locations.

A possible Venus exploration gizmo: either an aerobot or a stationary lander that needed a source of artificial light to do spectroscopy despite the incessant IR glow could have microprojectiles that contain nothing but a flash device. This need not require any wet chemistry or electronics whatsoever, or very minimal versions thereof, and therefore be extremely simple and light. An aerobot could drop them, or a stationary lander could eject them several (tens of?) meters away, and then the main craft would image the surface at the time/place of the flash. To get the purest signal, this could be done at night, when only the venusian IR glow would persist. Of course, with-flash and without-flash data would help to get rid of the noise. Perhaps this adds nothing to the LIBS approach -- the question is whether a laser casts its light farther and cheaper and more multispectrally than a "bottlerocket" style of flash. The laser could be used more often, but the flash would allow work at a distance to eliminate all of the scattering problems of the laser and half of the atmospheric absorption. Perhaps an aerobot that is not configured for Venus surface heat, but stays a few km up, could make use of flashes in a circumstance where a laser would require a lower and hotter "perivenus"? Just a thought on the behalf of 13th century technology.

Posted by: Myran Jul 1 2005, 04:31 PM

I think you are right, a Mössbauer spectrometer of the kind the MER rovers have will not do, whatever instruments a Venus lander will be provided with they need to work rather fast.
Perhaps the robotic arm should work by a simple cog and wheel system moving automatically from point to point and a simple contact that turns of the downward movement as soon it touch hard soil, just in the hope it will get to touch down on more that one kind of mineral and bedrock. Without computerized parts, you wont risk overheating and failure.

If one airconditioned lander survives the first 12 hours or whatever, it should have the ability to download new instructions, so this would indeed be a workable kind of lander.
But I have a hunch that the space agencies never will spend that much money to send any simpler lander that Phil Stooke suggests. When they spend that many millions for the launch and logistics, the administrators will upgrade the lander up to the point where the lander will be one other megabuck marvel in itself.

So that proposal of a really simple non computerized system and Phil Stooke's suggestion might not happen at all, yet I have a hunch that for one inhospitable place like Venus, the best way to go is by the 'keep it simple stupid' thinking.

Posted by: BruceMoomaw Jul 1 2005, 11:28 PM

The main justification for simplifying a Venus lander is that it can enable you to launch more than one at one time. Larry Esposito's "SAGE" concept -- which, from what little I know about it, apparently DID have both an airlock and a GCMS atmospheric analyzer -- neverthless consisted of two or three landers on one mission.

Posted by: AndyG Jul 7 2005, 02:39 PM

Given that the surface is so hot and so highly pressured, why not take a leaf from the early explorers of the ocean bottoms? Dredge for rocks!

Picture a balloon flying in Venusian atmosphere at about the 32km level. This height is good since it's below the bulk of the cloud cover, giving you the ability to view the surface. Pressure is around 8bar and the temperature is around 200C. Not really a problem for well-designed electronics & balloon materials. Water doesn't automatically boil at this pressure/temp, so may be useful for radiators.

A thin titanium wire, with a basic end effector, could be winched down from a balloon at this height to pick up suitable rocks for analysis back within the balloon. A wire some 1.32 mm across, tapering to around 1mm at the bottom, would in total mass about 160kg, and enable a load of about 20kg to be lifted, assuming some 5kg mass for a grabber/hardened camera, etc.

100kg of lift in a CO2 atmosphere could be provided with just under 8 cubic metres of H2 in the balloon, so the size of the bag could be really quite trivial.

Andy G

Posted by: Bob Shaw Jul 7 2005, 02:54 PM

As there are some fairly well-described outline designs for RTG-powered refrigerated landers, I find myself wondering whether the waste heat from the refrigeration system could be used to produce lift in a hot-air balloon. An almost mechanically inert (in terms of externals - obviously, there's pumps and whatnots beavering away inside!) lander could drift around the landscape, rising from time to time then falling once more. Think of a Galilean Thermomoter, and the way the glass spheres bob up and down...

You'd get:

Multiple ground-truth sites
Aerial imaging
Meteorology

And probably a few other goodies, too!

Posted by: JRehling Jul 7 2005, 08:18 PM

It'd be great if it worked, but of course, the refrigeration scheme itself involves a lot of mass per payload mass.

Venus permits a lot of buoyancy, potentially, especially if helium filled the balloon, but that margin could be eaten up with a nuclear-powered refrigerator + thermal insulation + ???

Also, heated CO2 would not give you much buoyancy compared to helium unless you really heated the hell out of it. Venus's high ambient temperature really works against that. To halve the density of CO2, you'd have to double the temperature, up to roughly 1000K! I'm no material scientist, but I guess you're talking about fewer and fewer possible balloon materials that will hold up as a strong, thin film when boosted to white heat!

I think compressing and uncompressing helium (at thermal equilibrium with the outside) would provide a *lot* more lift with less mass. Although, I understand and admire you're looking for synergy between a design side-effect and a possible desirable feature.

The synergy you get in design with Venus balloons is that the higher a balloon resides, the cooler the ambient temperature that must be withstood. If thermal inertia (passive!) can keep the system alive throughout a single exploratory drop, then we might have systems that can only tolerate the Venusian surface environment temporarily, but long enough for an arbitrary number of descents. The Veneras operated in this fashion. A balloon carrying a heat sink could reach thermal equilibrium at 40-100 C. Then the question is: How much time would be required in a surface stay to do useful science? For imagery, very little. To grab a sample, very little. It is possible, in times of favorable geometry, to work a single telemetry/command feedback loop with Earth-based controllers in just a few minutes. (Transmit an image, ask which rock/soil unit should be grabbed, and receive that command -- the AI for that is beyond MER, but not beyond reason.) If a ~45-minute surface stay is well within safe margins for thermal constraints, then that's not a bad MO. If descents could be managed at roughly the rate of one per day, then a lot of surface exploration could take place in a primary mission of two or three weeks.

The whole scheme then could be to identify a swath across one line of latitude of Venus that contains several worthwhile terrain units that are, moreover, going to be in local daylight with a line-of-sight to Earth during a desired primary mission. The craft would control its horizontal motion by ascending into local winds, thereby deriving the horizontal motion. The heat sink would get well below top operating temperature, and then the craft would perform a dive to its target. It would take descent images and a single surface panorama, beam them to Earth, and autonomously perform surface science while awaiting a command from Earth identifying which surface patch to sample by arm. After about 20 minutes, the human-made decision would reach the craft, an arm would make a grab for the target, and then the craft would ascend again, and spend its time analyzing the sample up in the cool heights above. An exploration of terrains in the vicinity of 150 E, moving along the equator or 10 S -- could be a heck of a mission, with lots of geological and "remote" sensing of many terrains. Of course, if a pair of these things could be afforded, working at different latitudes but identical longitudes in the same time frame, then a very thorough exploration would result.

Posted by: BruceMoomaw Jul 8 2005, 01:58 AM

Actually, this type of mission -- a balloon using "reversible fluids" to achieve controllable variable buoyancy with a surprisingly low use of both gas and power, spenjding most of its time in the clouds but dipping periodically all the way to the surface briefly -- has been studied by JPL for years as the "Venus Geoscience Aerobot". I've just found two very detailed descriptions of it that I wasn't even aware were on the Web (including Martha Gilmore's article, of which she privately sent me a less developed version YEARS ago. Apparently it took her that long to get Acta Astronautica to publish the damn thing.)

http://techreports.jpl.nasa.gov/1999/99-0750.pdf
http://www.planetary.brown.edu/planetary/documents/2056.pdf

If this balloon design is workable, then obviously this has tremendous merit as a New Frontiers or Small Flagship mission. (One can easily conceive of an improved version, which uses LIBS and Raman spectrometers for its brief surface analyses rather than an X-ray spectrometer as she suggests -- or which actually deploys a core tube or scoop to snatch a surface sample for later leisurely onboard analysis, like JPL's recent Titan Organics Explorer concept: http://www.lpi.usra.edu/opag/feb_05_meeting/presentations/beauchamp_%20presentation.pdf .)

Unfortunately, that seems to be a a very big "if", judging from Kerzhanovich's recent LPSC piece ( http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1223.pdf ), in which he says flatly: "A key problem is that at the time the decadal survey
was published, no high temperature balloon technology existed to implement either mission. Prior technology development efforts had concentrated on a
single balloon that could operate across the entire 0-60 km altitude range, tolerating both the sulfuric acid aerosols and the extreme temperatures of -10 to +460 ºC. However, this problem was unsolved because no combination of sufficiently lightweight balloon material and manufacturing (seaming) technology was ever found to tolerate the high temperatures at the surface." If, as this implies, polybezoxasole can't be adequately seamed after all, then we're stuck with his suggestion for a near-surface steel-bellows ballon whose instrument package must endure Venusian surface tempartures for o very long periods -- which will require new electronics technology, as the Solar System Roadmap says.

Posted by: Bob Shaw Jul 8 2005, 02:47 PM

Bruce:

Very interesting - you are a fount of knowledge!

The nice thing about hot-air balloons is that they have a natural homeostasis, and can tolerate leaks so long as you can keep adding heat - pressure altitude bursts etc are also naturally avoided by virtue of the big open cavity. Some of the recent terrestrial around-the-world (etc) manned ballooon flights have also used hybrid structures, with a helium bladder surrounded by a hot-air envelope.

As for materials, an open-bottomed stainless steel structure could be extended at altitude when cool (think of one of those nested metal travelling drink cup affairs crossed with an umbrella made out of Webb Telescope hexagons), with some sort of caulking around the edges like an intumescent strip on a fire-door and then used as an aerobrake to the surface. On the way down, it heats up, the caulking melts in place, the metal expands and suddenly there's a balloon. Well, a balloon made for a deep-sea furnace, anyway...

If there's an active refrigeration system aboard the lander then it'd run *hot* at the radiator end - the darn thing'd have to be much hotter than ambient, and that's red heat, so we're looking at a ready energy source for bobbing around the landscape, even with CO2. The killer would be to get up into the cool air again to dump as much heat as possible, or else you'd end up floating at some gradually decaying height while your electronics and mechanicals slowly baked. Think of the remote sensing fun at 5kmh at 300m altitude for a month, though!

Speaking of balloons, have you ever come across any serious commentary on the VEGA Soviet/French balloons? About all I've found are brief mentions...

Bob Shaw

Posted by: Bob Shaw Jul 8 2005, 03:03 PM

Among the interesting points in the .PDFs to which Bruce posted links are:

A wind-turbine to provide power for night-side operations

Pre-ordained trajectories for geological traverses

Very-high resolution surface imaging

Posted by: Bob Shaw Jul 20 2005, 01:45 PM

A conceptual small Venus atmosphere probe picture from 1979, intended to allow a slow descent of a (fairly) long-lived vehicle under a balloon.

Posted by: remcook Jul 20 2005, 01:53 PM

ESA is looking at a mission that is using a balloon that will stay afloat by dropping microprobes along the way. So you get both balloon and probe. Pretty neat idea.

found a website...

http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=35987

Posted by: BruceMoomaw Nov 6 2005, 02:15 AM

NASA's Venus Exploration Analysis Group (VEXAG) -- the new equivalent of MEPAG and OPAG -- held its first meeting yesterday in Pasadena ( http://www.lpi.usra.edu/vexag/vexag.html ). While I missed the morning session because I had to catch the final part of the COMPLEX meeting, I did manage to catch the afternoon session.

Unfortunately, not much was said then -- except that the subgroup that deals with "Planetary Formation and Evolution" (that is, surface studies as opposed to atmosphere studies) came up, during a session at the meeting itself, with what Steve Mackwell regards as a very good initial list of desired science measurements, along with information on how technologically difficult they will be. In the next two weeks, the subgroup will prioritize and finalize this list, and he's promised to send their conclusions to me -- although I imagine I'll be using those in my "Astronomy" article and so may not be free to announce them here. (I will say that he agreed with me that, since the minimal estimate for the cost of a Venus sample return is $10 billion, Congress will fund that mission on about the same day that O.J. finds the real killers. We will have to settle for in-situ measurements instead.)

Mewanwhile, three of the Powerpoint presentations from the meeting have just been put on its site at http://www.lpi.usra.edu/vexag/1st_comm_meeting.html . Three of them are disappointing, but there's a very nicely detailed description of the precise measurments that MESSENGER will make during its second Venus fyby in June 2007. (The instruments will be off during the first one in Oct. 2006, because it's near solar conjunction and the flyby is rather distant anyway).
http://www.lpi.usra.edu/vexag/Nov2005/MESSENGER_VEXAG.pdf

Posted by: JRehling Nov 6 2005, 06:29 AM

I haven't seen anyone note this yet, but this means that two spacecraft will be operational near Venus at the same time, as Venus Express will be near the very end of its primary mission. Very analogous to the simultaneous readings at Jupiter in December 2000 by Galileo (in orbit) and Cassini (just passing by). Venus isn't as lively in a particles-and-fields way as Jupiter is, but it sets up some nice opportunities for synergy. Interestingly, *three* US spacecraft were at Venus in 1990, when Pioneer Venus was late in its extended mission, Magellan was in checkout phase prior to the beginning of science operations, and Galileo flew by. In 1978, two Soviet landers arrived while a US orbiter and five entry probes, crowding the planet with *eight* pieces of hardware within a short time. But it'll be almost seven years between the brief Cassini flyby of Venus and the arrival of Venus Express. We are very fickle with regard to the closest planet.

Posted by: remcook Nov 9 2005, 10:01 AM

a good update from emily on oncoming missions (VEXAG meeting):

http://planetary.org/blog/article/00000038/
http://planetary.org/blog/article/00000039/
http://planetary.org/blog/article/00000041/

I didn't see this posted before...

Posted by: BruceMoomaw Nov 24 2005, 03:23 PM

To my delight, last night I stumbled by chance across something I've been looking for all year -- the new address for JPL's file of Technical Reports ( http://trs-new.jpl.nasa.gov/dspace/ ). And the very first article I found there was something I've been trying to find for a couple of years: the first good description of Larry Esposito's "SAGE" Venus lander proposal for the last New Frontiers AO ( http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38184/1/03-2520.pdf ).

While it didn't make the cut for finalist, it looks like quite a well-designed mission, featuring two landers that would touch down about 1000 km apart -- one on the tessera at Aphrodite, the other on the regular basalt plains to the south -- and survive for 1-2 hours each on the surface, consecutively transmitting their data to the carrier spacecraft while it made a distant flyby of Venus. The landing system is very much like that for the Veneras. There were seven onboard experiments -- including three atmospheric ones, but not including any attempt to track Venus' cloud-layer winds with a balloon (one originally stated goal for the New Frontiers Venus mission). A drill would collect a sample for X-ray spectrometry and diffractometry -- which makes me wonder whether the size and cost of this mission could be lowered by instead using a LIBS/Raman setup for surface analysis, thus allowing removal of the heavy drill and airlock setup. (It's stated that if it ever became possible to add a third lander, it would be aimed at a "hot spot", by which they presumably mean one of the relatively young volcanic highlands.)

One thing is noted which I should have thought of before but didn't: thanks to Venus' slow rotation, any direct-entry lander mission launched during a specific launch window is very limited in its scientific selection of landing sites as compared to a Mars direct-entry lander.

Posted by: BruceMoomaw Nov 24 2005, 03:26 PM

One other thing which I just now noticed on the last page: this mission may have been rejected not because of technical flaws, but simply because it didn't have any workable Venus launch window during the time specified for the launch of New Frontiers 2!

Posted by: Phil Stooke Nov 24 2005, 04:10 PM

I just tried to access the Venus lander PDS file Bruce linked to, but got the message that the file was damaged and could not be opened. Is anyone else getting this?

Phil

Posted by: BruceMoomaw Nov 24 2005, 10:10 PM

It just came through OK for me again (using the URL in my message as printed here). Must be your computer.

One can think of other ways to slim down this mission, too -- related to the decision to put the two atmospheric composition experiments on BOTH landers, although the atmosphere's composition will vary little or none from one place to another. One is a UV spectrometer -- presumably to try and identify the still-mysterious dark UV cloud absorber -- which is mounted outside the pressure hull and will burn out below 50 km; it could easily be removed from one lander.

The other is a GCMS which is mounted inside the hull and will operate down to the surface. Now, shrinking the pressure hull on one lander just to get rid of this instrument would surely cost more in design and manufacture problems than it would save -- but back in the very first round of Discovery selections, Esposito proposed a "Venus Composition Probe" in which both the UV and the mass spectrometer were mounted outside the pressure hull and only worked at high altitudes. All the composition data in Venus' lower, hotter atmosphere was obtained from a near-IR spectrometer inside the pressure hull, since it could sense all the chemically reactive trace gases we're interested in measuring at lower altitudes -- whereas the other trace gases (and especially isotopes) that we want to get better data on are pretty evenly mixed and so a mass spec can measure them in the upper air. The same could apply to the SAGE mission (which includes a near-IR spec for both atmospheric and surface composition data). Or, of course, we could put the atmospheric experiments on a separate, Discovery-class probe.

Do that, and replace the XRS/XRD with a LIBS/Raman setup, and you could get rid of ALL this probe's necessary openings to the outside hot air in its pressure hull -- all you'd need would be sealed electrical cables and fiber-optic lines. You could also greatly cut the time that it must survive on the surface, and analyze far more than one surface sample in that short time. (A motorized arm with a sensor head on its end, hooked up to fiber-optic lines leading to the various surface instruments -- including the onboard microsope, which in the current design can only look at one spot of ground -- could pat the surface at a whole range of points to analyze them in just a few minutes each; and the LIBS and near-IR spec -- and maybe the Raman -- could also operate through the same periscopic mirror as the panoramic camera to observe different, more distant spots on the surface.) I don't know how much worse a Raman is than an XRD in analyzing mineralogy -- I gather it isn't good at measuring the oxidation state of iron minerals (although the near-IR spectrometer might get good enough data on that), and I've found a fuzzy reference suggesting that Raman is worse than XRD in measuring the precise quantities of various minerals, as opposed to just confirming their presence or absence. But it's a possibility.

Posted by: Phil Stooke Nov 25 2005, 02:22 PM

You're right, Bruce... tried a different machine and I got it OK. And look at that - more points on the map. That's what I always want to see!

Phil

Posted by: JRehling Nov 25 2005, 05:22 PM

To put a finer point on it, I think the real problem is the Venus-Earth synchrony. The slow rotation constrains landing sites for a given launch window. More serious is that other launch windows will offer the SAME landing sites. Basically, minimum-energy trajectories offer up the same serious constraints, which is why all Veneras landed in a narrow longitude range. The main way around it is would be to spend a little more energy in cruise, so as to get to Venus sooner or later. Alternately, some gravity assists could be used so as to get to Venus, but at a different point in its orbit.

Posted by: BruceMoomaw Nov 26 2005, 02:27 AM

Remember Magellan, which completed 1.5 orbits around the Sun before intercepting Venus halfway through its second orbit -- the reason being simply that otherwise the Shuttles carrying it and Galileo would both have had to be launched in the same launch window to Venus. But this also meant a 6-month difference in the times that the two craft reached Venus, so that a lander on Magellan could have been dropped off at a completely different place than a lander dropped from Galileo with its direct trajectory to Venus.

Posted by: vjkane2000 Nov 26 2005, 06:31 AM

If you take Bruce's ideas on slimming down the mission to their logical conclusion, you could have a probe with just a descent imager and Raman spectrometers/LDS on one or more arms. (And probably an imager to see what the arms touch down on.) Such a probe could be very slimmed down -- perhaps enough that you could drop 4-8 on a single mission. Don't know whether this is better than the original mission idea. Have to think that the scientists/engineers would have thought of this one, too. Getting the sample inside to cooled instruments must be pretty valuable.

Posted by: BruceMoomaw Nov 26 2005, 08:24 AM

This wouldn't make the SAGE landers that much slimmer -- take a look at the table of experiment weights and power requirements in the JPL paper.

One possibility that comes to mind, though, is scattering a bunch of probes around on Venus that don't have imagers of any type (in addition to some that do), in order to get purely compositional data from the surface at a number of places for comparison purposes (along, perhaps, with a penetrometer or densitometer on the sampling arm so that we could tell how hard the material was that they were sampling). The data transmission requirements would be so much lower for these that they could send all their data directly back to Earth, very greatly simplifying the mission. And in that case you really would get a much lighter overall spacecraft capable of carrying more landers.

I'm currently awaiting my copy of a document that will be put out in a week or two by a study team for VEXAG (the Venus Exploration Analysis Group, part of whose Pasadena meeting I caught on the way home from the COMPLEX meeting) listing the scientific priorities and technological difficulty of various Venusian surface measurements -- which should tell us a lot more about the proper way to explore this very difficult subject. But there seem to me, right now, to be two (maybe three) top-priority items for Venusian surface analysis (since seismometry is very hard and must be bumped well into the future).

The first is trying to determine where there are any rocks or minerals indicating that early Venus had oceans -- including felsic (granitic) rocks and possible aqueous minerals. And the only good places to look for that evidence seem to be the tesserae and Ishtar Terra (the only thing on Venus that looks somewhat like an Earthly continent). The second is trying to age-date different parts of Venus to see whether the "catastrophic resurfacing" theory is correct, which might be doable, at least loosely, with in-situ instruments. But Bruce Campbell thinks that age-dating may not be possible even for returned Venus samples due to their high temperature (although others disagree with him), and that a better way to solve this problem is with an orbiter with a deep subsurface radar sounder to look for lava-flow overlay patterns in different types of terrain -- just the sort of mission he's proposing for the next Discovery AO.

The third is to try and determine the nature of that mysterious highly radar-reflective stuff that turns up on Venus' high-altitude terrain, which a single lander with additional goals might be able to do without very complex instruments. In short, answering all the really important questions about Venus -- until we can develop that difficult long-lived lander technology at our leisure -- may not require all that many landers.

Posted by: vjkane2000 Nov 27 2005, 06:08 AM

I don't think anyone would fly a lander without a simple descent imager. The imagers weigh, as I recall, ~300g, although the window might add weight. Assume that you put a second window/imager to look out where the arm touches down. The multiple imagers could share much of the electronics.

I remember a very old (30 years?) NASA technical study of follow on missions to Venus Pioneer. One of them included a derivative of the small probe that touched down and put out four arms with composition probes on the end.

I'd love to see a number of lander on Venus to explore the range of compositions.

Posted by: JRehling Nov 27 2005, 07:13 AM

The tesserae themselves may turn out to be a kaleidoscope of numerous former surface units. Which would mean that a stationary lander could tell us all about one speck of Venus and miss entirely the intriguing units only hundreds of meters away.

I think when we get serious about exploring Venus's geology, we're going to find it no simpler than, and potentially far more complex than, that of Mars, which still confuses us after the fifth significant landed mission.

Given the difficulties that orbiters are inevitably going to have, the limited sampling range of stationary landers, and the profound difficulties in building a Venus rover, an aero- mission of some kind has to come up soon in the planning process, even if it's only to get some multispectral descent imaging. I fear that until some multispectral descent imaging shows us what we can see from below the clouds, and what we can't, it's a mistake to invest too much in missions that may go to great lengths to acquire data that could be had in less detail but much greater spatial coverage from 20 km up.

Posted by: edstrick Nov 27 2005, 09:51 AM

I'd be really interested in knowing the calculated atmospheric opacity between 45 km altitude (just below the lowest observed cloud and haze layers seen by entry probes (more or less) and the surface as a function of wavelength.

We are going to try surface composition variation detection from above the clouds with Venus Express, using infrared that filteres up through the clouds in the atmospheric low-opacity windows, but there will be "no" resolution on the ground.. Basically a 50-some km blur from the 50-some km high main clouds

Below the clouds, you have a nearly aerosol-free view down to the surface, with gas absorption, scattering, and near the surface, emission. But at wavelengths long enough that Rayleigh scattering is less than 1, you can image the surface directly with optics-limited resolution.

Posted by: BruceMoomaw Nov 27 2005, 09:55 AM

First: it's not the WEIGHT of imaging cameras that's the problem -- it's their huge data return, which requires a flyby or orbiter craft to serve as a com relay. Get rid of imaging, and the landers can relay all the rest of their data directly back to Earth, which greatly simplifies a mission. (There was a debate about this for giant-planet entry probes at COMPLEX, in which Tom Spilker did a very good job of shooting down Scott Bolton's enthusiasm for the idea. But the technical problems that make it hopelessly impractical for the giant planets -- mostly because of the difficulty of having the probe enter at a place that allows DTE transmissions without it having to make a destructively steep dive into the atmosphere -- don't apply to Venus, as we already know from Pioneer 13.)

As for the tesserae, they seem to be areas that have been faulted by being stretched in one direction and squeezed in another (not at the same time), but there seems to be no evidence from their radar appearance that they're actually patchworks of small areas of different materials laid down at different times. It is, however, quite possible that -- if they really are the oldest areas on Venus, and date back to a time when it still had oceans, crustal tectonics, and the start of the formation of granite continents -- they really are a complex mixture of materials. In any case, the way to start investigating this seems to be simply to land on a couple of different tesserae -- or, again, Ishtar Terra, which is a very high-altitude plateaus that seems to be geologically unique on Venus -- with simple fixed landers and see if dramatic compositional differences show up.

And as for aerial observations, keep in mind that any probe too high to illuminate the surface with a flashlamp will only be able to see reflected near-IR sunlight in the five narrow spectral bands which Venus' clouds and air allow to reach the surface at all. (It's the same kind of problem that Cassini or a balloon have for near-IR mapping of Titan.) Those five bands will provide some useful compositional information, but not a really big amount (Kevin Baines discussed this several years ago in "Icarus"), and so it might be better to put such a multi-channel photometer on a balloon in the lower clouds rather than on a lot of separate descent probes. As for descent imaging, it obviously also has its uses -- but, again, to decide where to send surface-composition landers we might get better advance reconnaissance information from a really high-resolution SAR map made by a follow-up orbiter to Magellan, such as has been talked about. (A SAR orbiter capable of obtaining 25-meter resolution images may be doable for costs on the Discovery/New Frontiers borderline.)

Posted by: Phil Stooke Nov 27 2005, 09:32 PM

Bruce said:

"One possibility that comes to mind, though, is scattering a bunch of probes around on Venus that don't have imagers of any type (in addition to some that do), in order to get purely compositional data from the surface at a number of places for comparison purposes"

One problem with doing this without a camera is that you may not know the local geological context of the sample you get. Many tessera areas, for instance, have small patches of basalt in low spots, and many plains areas have small cones, ridges or patches of older material protruding through the plains material. Which material are you sampling? The Venera images and compositions we have are compromised a bit in usefulness because it's not really possible to relate them to specific geological units.

Bandwidth is a problem, but it's less of one now than it used to be - not long ago the idea of transmitting a heavily compressed image was anathema, but now it's done quite often. We would be better off with descent imaging, even if horribly compressed, in order to get the exact location of the landing site. And images can be compressed a lot these days.

Of course I'm an image guy so I may be biased!

Phil

Posted by: BruceMoomaw Nov 28 2005, 02:09 AM

But, once again, a high-resolution radar orbiter -- combined with the improved tracking that we have now over that for the Veneras -- could identify the landing sites for such landers with enough accuracy to enable the overall geological context of their samples to be determined. (After all, the phenomena Phil describes have been detected entirely on the basis of the Magellan images.)

In that connection, how do you know that there are "small patches of basalt in low spots" in the tesserae? Are these relatively crack-free patches, presumably laid down by later lava flows in the tesserae?

Posted by: tedstryk Nov 28 2005, 03:01 AM

Another possibility is, if the probe transmits at a very high rate, is that after landing, better versions of the images are returned with little loss.

Posted by: Phil Stooke Nov 28 2005, 03:34 AM

Bruce, yes, lots of tesserae have small ponds of lava in low spots, and fingers of it extending from the plains, a common embayment relationship. They show up clearly in Magellan images, but please don't ask me to unearth one right now! There must be patches of aeolian sediment, dark parabola material or ejecta in low spots, or other complicating factors as well.

The trouble with the high res radar is that, yes, you get better images, but no, you still don't know exactly which spot the lander came down on. Only descent imaging can do that for you, or the very difficult task, likely to be almost impossible on Venus, of matching features in surface panoramas with orbital images. There is no other way to locate a landing site exactly at the scale needed for knowing its geological context. Of course this does not apply in the case of homogeneous plains. In tesserae or any other complex landscape you are still better to go with descent imaging if at all possible, using heavy compression if bandwidth is the issue. I just ran a test, and I can easily reduce a 1 MB TIFF to 25K without compromising its usefulness for site location, probably smaller.

Phil

Posted by: vjkane2000 Nov 28 2005, 03:34 AM

I'm with Phil -- there are really good compression algorithms today that could be used. And you learn so much more if you understand what you landed on (are you measuring dust or a pebble or a lava plain?). If you really don't like having a relay craft, consider that a single image 1000x1000 image could be returned at ~300 bits/second (assuming 8X data compression). Probably not that unrealistic given today's communications technology at both ends.

But I think that the relay more than makes up for the extra complexity. I do remote sensing for my graduate work. Even 30m pixels are incredibly frustrating because they hide so much detail. Venus coverage is even worse.

If you have the relay craft and a roughly 3 hour communications window, you could imagine a mission that takes 30 minutes to descend to ~20 km above the surface, release a paraglider chute, take the next hour to take a transcect of images across the surface, and then have 1.5 hours on the surface.

Posted by: edstrick Nov 28 2005, 06:16 AM

The frustration of understanding anything about the geology of the Venera Lander sites is the utter lack of geologic context for the surface panoramas. Three "DIMES" type images, taken at 1, 5 and 20 (for example) kilometers with a 45 degree field of view, from my perspective, is almost mandatory for any understanding of the geologic context of chemical/minerological measurements from a lander.

It's lack -- we've only approximately located the landing sites of Venera 8, 9 and 10, 13 and 14, and Vega 1 and 2 -- in providing real geologic context has led to essential uncertainty on what geology some of those landers are on. Some are just not well located in regions of complex geology, Venera 8 in particular.

Radar data, by it's inherent nature, tells a lot about surface materials physical configuration: relief, roughness, texture, internal scattering, etc, but almost nothing about chemistry. In addition, it's remarkably hard at times to relate to visible geology. Witness the difficulty in relating optical observations of the Huygens landnig site to radar data. Shuttle radar penetrates a meter or so under sand sheets in the Sahara and show geology underneath you can't see standing there or in visible imagery from orbit. On a mission dominated by geochemistry-science, I'd prefer 3 good descent images over spiffy surface panoramas any time, much as I love a good pan!

Posted by: RNeuhaus Nov 28 2005, 03:20 PM

Why does not do design a good space architecture as the Mars ones with the initial support of MGS and Odyssey as the initial recoconizance support and as relay for the landed probes to Earth?

This architecture should be applied for the next mission to Venus and it would solve the communications problems to landed probes on Venus and also a better understanding of Venus in order to even assure the future missions to Venus. This mission be must taken with a gradual steps, perhaps, an lapse of 10 years.

Rodolfo

Posted by: JRehling Nov 28 2005, 04:51 PM

An orbiter for COM abilities would not have as much value for a world where landed missions only last two hours. In fact, an orbiter would be almost pointless, because it would only get to fly over the landing site once or twice while the lander was alive! You may as well land the COM package on the lander and send the high-gain telemetry straight to Earth instead of having it spend 90% of the lander's mission out of line of sight with the instruments on the surface.

Posted by: RNeuhaus Nov 28 2005, 08:42 PM

Let me see the architecture space design. As Venus rotates more than one year Earth. So the desired landing site can be programmed with anticipation according to the Earth's departure. So the lander will stay *almost on the same place facing to the Earth* for a long time so its HGA would be useful without much worries about pointing to Earth. So it is reasonably understandable that the COM orbiter is pointless unless a special or restrict conditions such as to land on the Sun's face.

Now, I am not very convinced that with our actual technology can permit to last the instruments less than 2 hours in Venus. It might be due to the economics factors. The cheaper ones will last less time than ones with more robust and expensive equipement incorporated with any kind of thermal refrigeration (LOX, LH, RTG, others).

Up to know, I don't still see a clear objective for the next mission to Venus. Indeed, it is still to early or not. The depending upon to the mission objective, It will be the factor influence for the right space architecture design. One group support for a ballute, others support for a landing of multiple probes. Any of them are useful but they bring the results for different objectives.

Rodolfo

Posted by: BruceMoomaw Nov 29 2005, 01:16 AM

I take for granted that the first three or four geological Venus landers will carry cameras. The question is just how many landers will be sent to other parts of the planet afterwards, and how many of them should also carry cameras. And since Venus (let's face it) is not burningly high on America's list of space priorities, it will be a long time before this question even becomes relevant.

The near-term question that IS relevant is whether we should send off a few geological landers right now (a la SAGE), or whether we should wait until we do a little more orbital reconnaissance (with radar and/or near-IR), after Venus Express, to select good landing sites for them. I don't begin to know enough science to judge this question, but I'll be interested in hearing what the VEXAG people say shortly.

Posted by: JRehling Dec 15 2005, 01:34 PM

A bit of terrestrial exploration of Venus: Christophe Pellier's images of Venus's nightside in the 2004 section overexpose the dayside in IR and you can faintly make out the nightside glowing from the surface heat!

http://www.lpl.arizona.edu/~rhill/alpo/venustuff/recobs.html

This is the first I have seen this in a photograph.

There have always been rumors of people seeing an "ashen light", seeing exactly this sort of spectacle, with the eye. Well, 1000 nm is certainly beyond the abilities of human detection, and I'm highly skeptical that anyone could see this with their own rods and cones.

Posted by: djellison Dec 15 2005, 01:38 PM

Ahh - Nico and I saw a presentation about that at the BAA conference this summer, there were some very good amateur observers there and they were amazed.

Doug

Posted by: Jeff7 Dec 15 2005, 06:33 PM

I suppose it might be possible - a few people can hear much higher frequencies than the average person. It doesn't seem too far fetched that we'd get the occasional genetic abnormality that would alter a person's visual spectrum slightly. But granted, stretching it all the way to 1000nm may be a bit much.

Posted by: JRehling Dec 15 2005, 09:21 PM

Well, it's not only how far out 1000nm is, but the fact that normal people have a greatly diminished sensitivity even at red. You can see a red laser in a dark room, sure, but a dim red light is much harder to see a dim green light of the same energy. Rods are only slightly sensitive to red light (they have about the same response curve peak as green-sensitive cones)... and when it comes to detecting *dim* red that happens to be right next to dazzling bright white (!) I am *very* skeptical. If the night side of Venus were somehow isolated from that bright crescent, I might believe it. Put another way, someone orbiting over the night side of Venus would have a much better chance of looking down and seeing non-black than someone on Earth looking into the bright crescent and seeing *dim* dark, near IR.

Posted by: Bob Shaw Dec 15 2005, 11:38 PM

A simple explanation for at least part of the story:

If the light reflected off Venus can cast shadows on Earth, then Earthshine must similarly illuminate the night side of Venus (remember the Clementine Lunar night-side shots, with the Solar corona and various planets in view, and think, if you will, how *dark* the surface really is compared to the white clouds covering Venus). Of course, at closest approach Venus is 100x further away than the Moon, so the effect will always be somewhat less...

If the Ashen Light waxes and wanes with Terrestrial cloud cover, then the case is settled (that phenomenon is visible on the Moon, and has been used to estimate changes in the overall albedo of the Earth).

I wonder whether Venus Express will be able to image the clouds of Venus by Earthshine?

Bob Shaw

Posted by: JRehling Dec 16 2005, 02:17 AM

Note that a full Earth is roughly 1/4 the luminance of a full Venus... but that's a crescent Venus that we see at its brightest. When the ashen light would be spotted, that would be a large gibbous Earth seen from the venusian cloudtops, so yes, the brightest Earth seen from Venus would be roughly the same luminance as the brightest Venus seen from Earth. Luna would add a tiny smidgen as well.

That said, although some nonzero amount of Earthly light would be shining off of Venus, the question is: is it visible? Again, I think the neighboring effect of that superbright crescent makes it unlikely. If I had $1500 and the goal of investigating this, I would create lab stimuli with Venus-in-telescope appearance and nothing but inky blackness inside, and see if subjects report that the space inside the crescent seems to be filled in. I would guess "optical illusion" before earthshine, or endogenous glow of somesort. I used to seriously research human vision, FWIW, but this sort of situation can not be abstracted from any published results AFAIK.

Posted by: BruceMoomaw Dec 16 2005, 03:17 AM

Yep. One would think that -- if the Ashen Light actually existed -- Pioneer 12 would have detected at least some faint indication of it during its 13 straight years in Venus orbit. I think the Ashen Light belongs in the same dustbin of history as Mars' canals and the Moon's transient glows.

Posted by: David Dec 16 2005, 01:48 PM

The Martian canals weren't entirely illusory -- certainly the network of fine lines was fictitious, but in many cases the "canals" were an attempt by the hand and eye to organize real but very small and faint albedo variations. Comparing old sketches of Mars with modern albedo maps is very instructive, both about the limits of human eyesight, and conversely, about the remarkable visual acuity and commitment of many of these early observers.

Posted by: BruceMoomaw Dec 16 2005, 11:27 PM

Well, it's a fact that E.E. Barnard -- one of the sharpest-eyed of all astronomers (which is how he discovered Amalthea) -- is also the only naked-eye astronomer to swear that he saw Mars covered with craters.

Posted by: Bob Shaw Dec 17 2005, 12:22 AM

There's an empirical test (for once), and that's the relationship between Terrestrial albedo and the (supposed) glow off the darkside of Venus - all that's needed is a small telescope for the Venus data and access to some carefully combined Terrestrial weather satellite images to prove or disprove the assertion.

Sounds like a PhD in waiting...

Bob Shaw

Posted by: David Dec 17 2005, 12:47 AM

I've read that claim attributed to John Mellish. It's a little hard to believe, unless you count the Hellas and Argyre basins as "craters", in which case they've been observed for a long time. Schiaparelli Crater's outline was observed, by Schiaparelli himself, but only because it cuts into the dark outline of Terra Meridiani (and of course he didn't identify it as a crater). It's hard to imagine anything smaller being resolved by early 20th-century telescopes, ideal viewing conditions or no. Even on Hubble images Martian craters are not very noticeable.

Posted by: dvandorn Dec 17 2005, 01:39 AM

One reason Martian craters are hard to see from Earth-based telescopes is that, as with most cratered bodies, they aren't very obvious except near the terminator. And we very, very rarely see much in the way of a terminator on Mars. Most of the Mars views from Earth are nearly full-disk, the terminator fuzzed by being viewed through the maximum amount of Mars atmosphere it's possible to have between us and the Martian surface, and by foreshortening.

The human eye has far better naked-eye resolution of the Moon than we had of Mars through telescopes for hundreds of years, and even so, lunar craters weren't really identified as such until people started looking at the Moon through telescopes. And we get very good terminator views of the Moon from Earth. So, even if we were able to see Mars with a terminator crossing mid-disk through cratered terrain, it wouldn't be surprising if we missed craters...

-the other Doug

Posted by: Phil Stooke Dec 17 2005, 05:21 AM

I think the whole issue of earth-based identification of craters on Mars is frequently misrepresented.

If I look up at the Moon without a telescope I can see Mare Crisium... it's a dark circular patch which lies in a crater, a big crater which we often call a basin, but a crater nonetheless. But I'm not seeing the crater, the depression, I'm only seeing the dark floor. I simply don't believe that Mellish or Barnard or anyone else ever saw a crater. They only saw - at most - circular albedo markings. The idea that they were craters was pure guesswork, based on the appearance of Plato, Crisium etc. on the Moon. The best proof of this is the case of Nix Olympica, a prominent circular bright spot, trumpeted as a crater when Mariners 6 and 7 appeared to resolve it as a crater with a central peak. But it wasn't.

Phil

Posted by: JRehling Dec 17 2005, 06:28 AM

To detect a dim object and to see fine details are two distinct skills, actually using two different portions of (and cell types on) the retina. I wouldn't know if the two abilities are positively correlated among people with non-troubled vision... they may even be negatively correlated.

Posted by: gndonald Feb 20 2006, 04:34 PM

The following are the best references I have found online:

http://www.mentallandscape.com/V_Vega.htm

The above covers the entire flights and the origins of the ballon plan. The following two pages from Astronautix.com provide additional information into the original VeGa plan, which would have seen four probes launched, two of which would have been dedicated ballon carriers.

http://www.astronautix.com/craft/vega5vs.htm and http://www.astronautix.com/craft/vega5vk.htm

Graham

Posted by: Bob Shaw Feb 20 2006, 10:11 PM

Phil:

I got new glasses the other week, and can easily persuade myself that I see Aristarchus (well, the plateau) with the not-quite-naked eye. Contrast helps, true - but *knowing* it's there helps a lot more!

Bob Shaw

Posted by: ljk4-1 Feb 21 2006, 10:20 PM

There was an article in Sky & Telescope magazine (exact issue I do not recall,
but likely within the last 10 years) that claims the craters he saw were actually
the Tharsis volcanoes.

But why were scientists so surprised when Mariner 4 found so many craters
on Mars? Did they really expect the planet to have more erosion mechanisms?

Posted by: Bob Shaw Feb 21 2006, 10:54 PM

George Pal put craters on Mars in the 1950s! So they must have been not far below the surface of the semi-technical consciousness...

Bob Shaw





Graham:

Thanks - none of these offer very much in terms of detailed construction, though...

Bob Shaw

Posted by: JRehling Feb 21 2006, 11:56 PM

We're way off the topic of Venus, but an issue from this past year offers evidence that the relief of Argyre had been observed. The article asserts that some previous analysis (perhaps the one you mention above) goofed by forgetting that telescopes invert images, and reported the southern hemisphere phenomenon as a northern hemisphere phenomenon.

Beyond doubt, the best ground-based telescopic observations in 2003 showed a shadow at Olympus Mons. But that was with adaptive optics.



Sure. It was known that Mars was pretty cold, but warmer than Antarctica. Antarctica is pretty well eroded. Of course, the whole story behind craters, impactors, and the rate thereof over the age of the solar system had not yet been established either. And the seasonal shifts in color on Mars hinted (correctly, but vaguely) as to SOME kind of activity there. It turned out to be dust... but dust that happens not to provide much erosion. Who could have guessed that?

Posted by: edstrick Feb 22 2006, 08:37 AM

There was a full set of preliminary science papers from the Venus balloon experiments and I'm pretty sure a followup set of primary science results, published first <I think> in Science, then maybe in JGR <Journal of Geophysical Research, not sure which series>.

Regarding the whole craters on Mars surprise. Remember that essentially up to the Mariner 4 Mission, the best estimates for the martian surface pressure were around 1/10 th atmosphere, not 1/100 th. Improved precision spectroscopy had just shown a pretty solid measure of C02 surface pressure of 1/100 or 1/200 atmosphere, but nitrogen or argon were undetectable. The new figures had gotten attention, but not universal acceptance. So the whole vague arm-waving ideas of Martian geology were implicetly assuming a more active geology and surface environment.

We STILL were caught flat-footed. Sometimes EVERYBODY misses the obvious, including the people who didn't miss it but didn't keep screaming... "Hey.. this is important".

Posted by: Phil Stooke Feb 22 2006, 01:34 PM

Replying to Bob about seeing Aristarchus with his new glasses:

Yes, but it's not Aristarchus the crater you're seeing, or the plateau, it's the Aristarchus ray system, which has much more contrast and is MUCH bigger. If you didn't know there was a crater in it, your observations would not tell you that.

Ditto Mars. Barnard, Mellish, Antoniadi - they were seeing spots and interpreting them as craters. Some were, merely because they had material of differing albedo on their floors. Some were not (e.g. Juventae Fons, Nix Olympica). They only saw spots.

Phil

Posted by: BruceMoomaw May 3 2006, 02:51 PM

The presentations from the second VEXAG meeting have just arrived ( http://www.lpi.usra.edu/vexag/May2006/presentations.html ). In the one on the latest update of the Solar System Roadmap ( http://www.lpi.usra.edu/vexag/May2006/VEXAG_52006_ELLEN.pdf ), Ellen Stofan's group recommends that for the projected Flagship-class Venus Surface Explorer, an "air mobility platform with long traversing" is now "preferred over a surface rover" for Venus, logically enough. (Not only does it allow much longer traversing, but in the case of Venus it would also allow the vehicle to land, hastily take a look around and grab some samples for later digestion, and then take off again for the cooler upper atmosphere, thereby reducing its heat burden.)

Actually, though, the single most useful presentation from this VEXAG meeting may be Larry Esposito's summation of our current scientific knowledge of Venus ( http://www.lpi.usra.edu/vexag/May2006/ChapmanSummaryVEXAG.pdf ).

Also see Emily's series of very useful blog entries on the goings-on at VEXAG ( http://planetary.org/blog/ ).

Posted by: RNeuhaus May 3 2006, 04:01 PM

I feel that the last proposal from VEXAG is more sensate and doable. So, I hope they will have a good common sense to agree and stick these objectives and start to work together without much missing time and money.

Rodolfo

Posted by: DonPMitchell May 4 2006, 08:33 PM

Bob, what in particular did you want to know about the construction of the Vega aerostats?

Posted by: Phil Stooke May 4 2006, 09:00 PM

Hi Don! That was quick!

Phil

Posted by: nprev May 5 2006, 12:40 AM

Mr. Esposito's presentation was indeed informative, Bruce; thanks for posting the link!

2 By of oceans, huh...hmm. Although this is wild speculation, you have to wonder if maybe the advent of photosynthetic life on Earth was what saved us from becoming Venus' slightly bigger sibling in all respects.

Still, if oceans did persist that long, why wasn't more CO2 captured as limestone to prevent a runaway greenhouse? Did Venus all of a sudden become enormously more volcanically active than Earth ever was, causing that 'global resurfacing event' and a CO2 overload in the atmosphere that the oceans just couldn't process fast enough?

Lots of interesting and potentially quite significant contingency scenarios here...

Posted by: DonPMitchell May 5 2006, 01:53 AM

Venus has almost no magnetic field, so like Mars, hydrogen has been preferentially blasted away by solar wind. It lost almost all its water that way. Venus also seems to have a lot more atmosphere than Earth, even taking into account carbonates in the Earth's crust. Perhaps the late collision that created the Moon, blasted away most of the original volatiles.

Posted by: BruceMoomaw May 6 2006, 09:22 AM

The current concept of Venus is that it was never quite warm enough to develop a genuine "runaway greenhouse", in which the greenhouse effect from all the water vapor initially in its atmosphere raised its temperature by a greater enough margin to evaporate a really huge additional amount of water into the air...and so on in a self-amplifying positive feedback that took the form of a diverging series that didn't stop until ALL the planet's water was in the form of atmospheric steam, after which enough of it soared into the upper atmosphere for solar UV to get at it and break it down.

Instead, it appears that early Venus was instead a "moist greenhouse". That is, its initial warmth was greater than Earth's by a relatively modest margin, so that the amount of additional water that was evaporated into the air by that warmth was also fairly modest and so produced only a small additional greenhouse effect...and so on, in a positive-feedback effect that took the form of a converging rather than diverging series and thus finally leveled off at a certain point (as indeed our own water-vapor-generated self-amplifying greenhouse effect does after warming Earth by a total of about 33 deg C).

This stabilized level of early Venusian warmth, however, was still high enough to loft the planet's water vapor to altitudes high enough that solar UV could break it down with tremendously greater efficiency than was happening on Earth even before our photosynthetically created ozone layer appeared. Thus Venus was still stripped of ALL its water supply after (according to the majority view) a few hundred million years, at which point its "carbonate thermostat" -- which depends on the existence of liquid water -- also shut down. That is: after Venus' liquid water vanished, all the atmospheric CO2 which had been turned into carbonate minerals by that liquid water got eventually dragged back down by the planet's still-functioning plate tectonics into its semi-molten asthenosphere, where the carbonates were broken back down into CO2, which was then belched back into the atmosphere again by its volcanoes -- and this time that CO2 did not get turned back into carbonates again, so that the volcanoes eventually belched the planet's entire large CO2 supply into the air as a permanent super-thick atmosphere whose greenhouse effect (even without the assistance of water vapor) was strong enough to raise its temperature to its current roasting level and keep it there.

The planet's plate tectonics, according to this model, did shut down a billion years or so after the planet lost all its surface liquid water. This is because mixing liquid water with rock greatly lowers its melting point -- and so, without water to do this, the planet's asthenosphere solidified and permanently jammed up its plate-tectonic conveyor belt. Thus there may still be some carbonates sitting around on Venus' surface that were not taken underground and broken back down into CO2, although most of them were thus destroyed before the plate tectonics shut down completely. But at any rate, there's no evidence that the advent of photosynthetic life did anything to prevent Earth from turning into a Venus-type oven -- we were safe from that fate whether life had ever evolved on Earth or not, simply because we were far enough from the Sun for virtually all of our atmospheric water vapor to stay trapped in our dense lower atmosphere by the "cold trap" of our stratosphere and thus be safe from breakdown by solar UV.

David Grinspoon has recently proposed an interesting variant of this idea, based on the assumption that the calculations of James Kasting -- which are what have led to the rejection of the "runaway greenhouse" model of Venus and the acceptance of the "moist greenhouse" model instead -- are (by Kasting's own statement, an upper limit) which ignores the possible cooling effect of the dense high-albedo water clouds which the initial warm Venus would have had. Grinspoon thus thinks that early Venus may have been cool enough that it didn't lose all its liquid water (and thus start building up a super-dense CO2 atmosphere) for fully 2 or 3 billion years -- and therefore that its plate tectonics may not have shut down until only about 500 million years ago, so that the fact that Venus' surface (in the opinion of most geologists) suddenly started retaining impact craters at that point was not due to a separate "catastrophic resurfacing" event at that time, but just to the fact that, before then, plate tectonics had been erasing most of the planet's craters just the way it still does for Earth.

As Grinspoon points out, one astonishing side aspect of his revisionist view of Venusian history is that Venus would have had time to evolve not just microbial life (which Kasting's classic moist-greenhouse view might also allow), but photosynthetic and maybe even primitive multicellular life -- unlike Mars, Europa, or any other place in the Solar System. Ah, but is there any chance that any fossils of such Venusian life could survive to the present day in such a savage environment? Now you can see one reason why geologists are so interested (as the 2002 Decadal Survey said) in looking for any evidence at all of surviving sedimentary rocks, carbonates, or other aqueous minerals on Venus' surface.

Posted by: PhilHorzempa May 7 2006, 04:39 AM

Thank you Bruce for reporting on Mr. Grinspoon's ideas. I think that he is one of
the more original and innovative members of the planetary science community.
I especially like David Grinspoon's proposal to include a manned mission to Venus,
as part of the VSE. As I recall, his plan calls for a crew to orbit Venus in a CEV and
use that vantage point to control a series of unmanned probes on the planet itself.


Another Phil

Posted by: Bob Shaw May 7 2006, 03:51 PM

Don:

I've only seen (a very few) poor quality illustrations of their design - they've always struck me as being one of the more fascinating unsung planetary missions (probably well covered in French, though!). It's primarily the general layout, the deployment, and suchlike which I'd like to learn more about!

Bob Shaw

Posted by: DonPMitchell May 7 2006, 05:37 PM

Blamont's book (in French) talks at length about this. The Vega balloon mission didn't have much to do with the French. In 1978, Blamont proposed an idea to send a much more complex mission to Venus that involved a big metal-foil balloon probe and an orbiter to relay its telemetry. As far as I know, nothing was ever built or designed in detail. The Mars sample-return mission was sucking the life out of their space budget though, so they sent the Venera-11/12 mission, and botched up some aspects of it. The head of NPO Lavochkin was fired after these probelms.

The Vega probes were designed at Lavochkin, based on a proposal by V. Linkin and others. It's made of teflon and nylon, and quite a bit smaller that what Blamont had proposed.

The idea of combining a Venus mission with a rendezvous with Halley's comet is from Vladimir Kurt. He and a mathematician worked out the celestial dynamics, and got it approved. Some kind of serious falling out occured between Kurt and Sagdeev though, so you don't see Kurt's name mentioned much, even though he was a primary mission planner for Vega.

Here is a diagram of the deployment:

[attachment=5484:attachment]

Here are a couple pretty good diagrams of the aerostat:

[attachment=5481:attachment]

[attachment=5480:attachment]

Posted by: tty May 7 2006, 06:00 PM

Plate tectonics don't renew the whole surface, only the deep ocean part. The continents (including the continental shelf) are too light to be pulled down in the subduction zones. If Venus once had plate tectonics the "continents" (highlands) should be more heavily cratered than the "oceans" (basins). Whether this also implies that fossils and carbonates should be preferentially sought for in the highland areas is uncertain. The last life would have been found in the deepest parts of the basins, but these may have been "reprocessed" before plate tectonics stopped (here on Earth the ocean bottoms are completely "reprocessed" after ca 200 million years).

Incidentally there is evidence that Earth also had a "moist hothouse", not once but three times and that it saved rather than extinguishing life here. In the Late Proterozoic (600-800 million years ago) Earth suffered a series of extreme glaciations when all, or almost all, oceans froze over and continents were glaciated even in near-equatorial areas. Such a "snowball Earth" is climatically stable since the high albedo reflects most solar radiation back into space. However volcanism continued and since the oceans were ice-covered and the continents frozen no CO2 could be absorbed, but rather kept accumulating for maybe 20-30 million years. Temperatures slowly rose until the ice finally started melting, the albedo went down, the ice melted faster etc in a runaway process that converted Earth from Super-Antarctica to Super-Tropics in just a few thousand years. In this extreme hot-wet environment chemical weathering became intense and CO2 was rapidly drawn down and vast amounts of carbonates were deposited right on top of glacial deposits - a most unusual juxtaposition.

As for whether fossils could survive such extreme conditions, the answer is probably yes. Fossils can occasionally be recognizable in rocks that have been heated to similar temperatures on Earth. However here such heating is invariably linked to great depth and extreme pressures and also not continued for such a long period (500 mya), so it is difficult to make comparisons.


tty

Posted by: Bob Shaw May 7 2006, 06:02 PM

Don:

Thanks!

I hadn't previously realised that the entry/deployment sequence was quite so complex - I'd presumed (for no good reason that I can think of) that the lander simply had a bolt-on atttachment which was the ballooon and whatever bits were required to set it going! It's really impressive that a clockwork spacecraft could do so much and so well.

Bob Shaw

Posted by: DonPMitchell May 7 2006, 06:10 PM

Yeah, the balloon and helium bottles were stored on a ring-shaped unit that wraped around the lander antenna.

The Russians were very good at clockwork. You wouldn't believe what one of those PVUs looked like! Think, miniaturized Babbage difference engine.

The main spacecraft had a real computer on it, but not the lander or aerostat.

Posted by: Bob Shaw May 7 2006, 06:14 PM

Couldn't get the parts, eh - no wonder Madame de Pompadour was so popular!

(don't ask)

Bob Shaw

Posted by: DonPMitchell May 7 2006, 07:13 PM

Hmmm, over my head. :-) I meant to type PTU (program timing unit). Starting to think in Russian...

Posted by: mchan May 8 2006, 12:52 AM

Over mine, too. IJFGI. Learn something new everyday.

Posted by: BruceMoomaw May 8 2006, 01:39 AM

This is why one of the biggest goals in Venusian exploration is whether there is anything on Venus that can be called "continents" -- that is, patches of lightweight granitic rocks floating on top of the basalt plates, and therefore resistant to being pulled down into the deep by crustal-plate subduction. Earth's continents are thought to be made of lightweight silica-rich melt rock that was produced and separated when Earth's original basalt was mixed with large amounts of liquid water while it was being pulled down into the asthenosphere and remelted -- so the existence and size of any continents on Venus is yet another factor that seems to depend on the size of any initial liquid-water oceans it had early on. (The 2002 Decadal Survey is very clear on this point -- find any large amounts of granite on Venus anywhere, and you have strong evidence that it had substantial water oceans early on.)

Thus the strong interest in using the future landers to inspect the two types of Venusian terrain suspected of being possible continents; the tesserae (which were the target of one of the twin landers in Donald Esposito's "SAGE" concept at the last New Frontiers submission), and the huge "Ishtar Terra" in Venus' north polar region.

(By the way, the JPL technical report on SAGE -- http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38184/1/03-2520.pdf -- implies (pg. 18 and 21) that the only reason it was rejected as a finalist is simply that its launch window to Venus didn't fit in with the assigned period during which NF 2 was supposed to be launched. If that's the only grudge they had with it, I think it will definitely be a front-runner for the NF 3 selection, whenever that is finally made -- espcially since the Inner Planets Subgroup of the 2002 Decadal Survey ranked a Venus lander as more important than a sample-return mission to the moon's Aitken Basin, and the only reason the Survey as a whole gave the latter such a high overall rating is that it said the automatic rendezvous and docking technology that they thought an Aitken Basin mission would need would be useful practice for a Mars sample return. As things turned out, the Aitken Basin proposal that was a finalist -- "Moonrise" -- didn't use unmanned R&D at all.)

I've read quite a bit about the two supposed "Snowball Earth" periods in the Precambrian, and the wild pogo-sticking in global temperature that's thought to have occurred during them. There are several explanations proposed for them -- ranging from continental drift breaking up an initial giant supercontinent to create a bunch of smaller continents with a larger total amount of shallow coastlines that thus pulled more CO2 out of the air by carbonate weathering, to the idea that the first photosynthetic cyanobacteria may have brought on one of the two crises themselves by producing enough oxyen to destroy the methane greenhouse that had been keeping early Earth warm. (And the latter, in turn, may perhaps have been originally created by the earlier generation of methanogenic bacteria!) There are still a few holdouts on whether the Snowball Earth episodes occurred at all, but the evidence seems to be growing steadily.

And as for the survival of fossils -- or at least microfossils -- under the savage surface conditions of Venus, there's a rather encouraging new LPSC abstract ( http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1028.pdf ) on the apparent ease with which biochemical fossil evidence seems to survive even in giant-meteor impact melts on Earth. But if you think a fossil hunt on Mars will be difficult, consider one on Venus...

Posted by: DonPMitchell May 8 2006, 09:08 AM

I'm not really a fan of either of his ideas. Carl Sagan suggested a long time ago that (Earth-born) microbes might be bred to survive in the Venusian clouds. Um, he probably says "Cytherean clouds". But that was in the early 1960s, before we knew better.

I'd be surprised if any molecule with more than a couple carbon atoms can survive in the Venusian atmosphere. Certainly there is no obvious sign of organics in the IR fourier-spectrometer measurments (Venera-15), while the Earth has clear CH-band structures. Keep in mind, the atmosphere of Venus is very dynamic-- convenction cells, high speed winds at the cloud level, etc. Those hapless microbes will alternate between being carried up into the zone of solar radiation, with no ozone or magnetosphere to protect them from every kind of ionizing radiation. Then down they go into the deep atmosphere to be pressure-cooked in suphuric acid. It's the kind of theory you propose to get your name spashed in the papers.

Then there is the manned orbiter around Venus. Kinda like ISS...except more expensive and dangerous. OK, now I said it, ..."ISS"

NASA is spending 4 times as much money as ESA, RKA and China combined. For $17 billion a year, just think about the kinds of science we could be doing all over the solar system. Rovers on IO, sample return missions to the planets and satellites, submarines under Europa. But here we with NASA wringing its hands, cancelling missions. Now why is that?

Posted by: Bob Shaw May 8 2006, 09:07 PM

Google 'Madame de Pompadour and Dr Who' - I'd just watched it! And put not your faith in clockwork!

Bob Shaw

(behind the sofa)

Posted by: BruceMoomaw May 8 2006, 10:09 PM

Aha! I always wondered why Madame de Pompadour came up with that ridiculous hairdo. She was hiding her TARDIS in it!

Posted by: Bob Shaw May 8 2006, 10:40 PM

Bruce:

Believe it or not, there are actually three or four left in Glasgow; or perhaps it's the same one...

Bob Shaw

Posted by: Chmee May 9 2006, 04:28 PM

So what exactly was the purpose of those Police boxes in the UK? Kind of an exclusive telephone booth for cops?

I watched Dr Who for years and never understood that.

Posted by: ljk4-1 May 9 2006, 05:56 PM

I think UK mailboxes look far more like alien robots.

http://www.irelandinformationguide.com/Image:RoyalMailCollectionBox20040124CopyrightKaihsuTai.jpg

Posted by: Bob Shaw May 9 2006, 05:56 PM

Yes - from the days before portable radios (they were designed in the 1920s). UK Police also carried whistles with a very distinctive sound, to call for aid (I always wondered what stopped the guys in the black hats getting hold of whistles in order to confuse matters, sorta like a 'whistle gap'!). Officer Dribble, er Dibble, in the classic Boss Cat cartoon show had exactly the same thing, but in his case it was just a phone in Top Cat's alley.

Bob Shaw

Posted by: BruceMoomaw May 12 2006, 08:08 AM

After clawing my way through my CD-ROM library of recorded Web documents on Venus, I find the following on Grinspoon's suggestion that Habitable Venus may have lasted a very long time. (There certainly must be more than these.)

http://www.aas.org/publications/baas/v35n4/dps2003/433.htm
http://sciencenow.sciencemag.org/cgi/content/full/2003/909/2
http://www.newscientist.com/article.ns?id=dn4136

And, on possible ways we might look for evidence of past liquid water on the surface:

http://solarsystem.wustl.edu/our%20reprints/1997/No79%20Zolotov%20et%20al%201997%20Icarus.pdf
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1152.pdf
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1992.pdf
http://www.aas.org/publications/baas/v37n3/dps2005/764.htm

Posted by: vjkane Jul 23 2008, 03:48 PM

Presentations from the last VEXAG meeting are now posted: http://www.lpi.usra.edu/vexag/may2008/presentations/

I found the presentation on the Japanese Venus Climate Orbiter and the Flagship mission analysis particularly interesting. The former is an imaging mission that will use a near equatorial orbit to achieve semi-synchronous coverage of the atmospheric rotation of the atmosphere.

The flagship report details the analysis for a possible 2020's (or so hoped) mission. As reported in the press, the proposal would include an orbiter (high resolution radar seems to be the key instrument), two landers with atmospheric composition capabilities and balloon ascent following sample acquisition, and two mid-altitude balloon platforms. Total cost is ~$3B (presumably in today's dollars).

Some thoughts on the flagship proposal:

The proposal seems to knock the legs out from under the New Frontiers VISE proposal, or any similar New Frontiers proposal. (This involved two short lived landers without balloon ascent.) This scale of mission receives the lowest science score. Yet for the price of two of VEXAG's short-lived landers (with balloon ascent), 4-6 VIS landers could be implemented.

The orbiter is actually fairly cheap, almost Discovery class, and would probably fit within that budget with some modest international participation. There's no claim in the presentation that there is much advantage to flying the orbiter with the other Flagship elements.

All medium altitude balloon options seem to cost ~$2B, as do the short-lived landers with balloon ascent.

VEXAG appears to be going to the full monty with a Flagship proposal. Yet, at best, Venus would be third in line after an outer planets flagship and a Mars sample return. Never hurts to make your request. But I would have two requests outstanding -- a high priority Discovery and a New Frontiers mission (fly something in the next decade) and a follow on flagship that might fly in the 2020s, and more likely (in my opinion) in the 2030s.

Posted by: Vultur Nov 15 2008, 07:49 PM

I think Venus rovers and balloons, someday, might be teleoperated by people somewhere closer to Venus.

Posted by: Enceladus75 Nov 19 2008, 07:58 PM

Whilst it would be brilliant to have rovers on Venus, I doubt they'd work with todays materials technology, given the scorching temperatures and crushing pressure on the surface.

Maybe a balloon/blimp could be a viable concept?

Posted by: PhilCo126 Nov 20 2008, 07:04 PM

Venus resembles a depiction of "Hell" so it will indeed be extremely difficult (read expensive) to get something working on the surface

Posted by: Juramike Nov 20 2008, 08:35 PM

The Venera landers did manage last about an hour on the surface.

I like to think that with all the improvements in instrumentation technology (and better luck), that a next generation lander could do great science even with only an hour of lifetime.

-Mike

Posted by: vjkane Nov 21 2008, 05:31 PM

The current lander plans seem to be counting on about an hour or two, so not much improvement there. However, there are a couple of ways of getting more science. First, you could grab samples, inflate a balloon, and do the analysis in the cool clouds. That is the official Venus lander goal for the New Frontiers Venus mission and I believe for the proposed Venus Flagship mission. However, it's recognized that that approach is expensive, so simply short lived landers are an acceptable alternative and were proposed for the first New Frontiers competition and are rumored to be proposed for the upcoming competition.

The other possibility is to use remote laser sensing (both a la MSL and Raman) to target multiple features at the landing site without the difficult problems of bringing samples inside the craft. My hope is that a periscope could sit atop the lander. An on board camera would analyze images of the site, identify a variety of targets, and target the laser accordingly.

I just posted a long discussion of possible New Frontiers Venus missions at http://futureplanets.blogspot.com/ that discusses these options and has links to proposed mission descriptions.

Posted by: huygens_stowaway Dec 4 2008, 09:37 PM

I'm definitely no expert on the surface composition of Venus, but I wonder if samples would undergo chemical changes when transported to a much cooler, lower pressure environment prior to analysis. Would any valuable science be lost this way?

Posted by: centsworth_II Dec 4 2008, 10:02 PM

I expect the collection system would seal samples off from the external environment. The samples would probably be very small.

Posted by: Paolo Jul 12 2009, 03:01 PM

An interesting http://www.lpi.usra.edu/vexag/reports/venusFlagshipMissionStudy090501.pdf

Posted by: qraal Jul 16 2009, 09:34 AM

Hi Guys

Geoff Landis discusses aerobots and surface rovers in some detail. New Silicon carbide electronics can operate at 500 C for hundreds of hours, so they'd be ideal for the rover...

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090001338_2008047211.pdf

http://www.lpi.usra.edu/vexag/may2008/presentations/18Landis.pdf

...such a mission would stretch the state-of-the-art, which is a worthwhile goal for NASA. Would also allow design of deep-probes for the gas-giants! Down to the 200 bar level on Jupiter, 300 on Saturn and 800 bar on Uranus/Neptune.

Posted by: MahFL Jul 16 2009, 12:35 PM

The Landis paper is really interesting, I did not realise electronics could operate reliably at 500 C.

Posted by: stevesliva Jul 16 2009, 03:52 PM

I don't think they can, yet. I think automotive applications are pushing silicon CMOS electronics to over 200C, and coupled with the reliability requirements of cars, they might start using SiC when it gets to the VLSI stage. Reading the paper, they fully admit that SiC has been played with at 500C, but only on the order of a single logical gate. Their comment, not mine, is that this is comparable with the state of the art during the Mercury program. Between now and when it's used on a spacecraft, someone needs to progress the technology from 10 transistors to a few thousand for a microcontroller. And validate both volatile and nonvolatile memories of some sort. If they get a flip-flop working at 500C, they're golden. The nonvolatile memory can be magnetic coils, Apollo-style.

...as I keep reading... Yup, they say memory is still a big unknown in SiC. Oh, and they say it's not yet complementary, so it's higher power than CMOS (where the C stands for complementary).

They also waffle back an forth about what would be heavier:
Electronics running at 300C and a big cooling system.
Or Electronics running at 500C and a smaller cooling system.

Personally, I'd bet that any mission in the next few decades doesn't have any large ICs running at 500C. I'd love to be wrong, though. Maybe private industry will find some application that needs it. Geothermal power or efficient furnaces or something.

Posted by: tasp Jul 16 2009, 11:25 PM

And recall, even with an electronic device operating at 500C, you still need insulators, conductors, capacitors, resistors, tuned circuits, etc. And to be able to resist a corrosive environment and high pressure.

This is quite a challenge from a materials engineering standpoint.

Posted by: stevesliva Jul 16 2009, 11:39 PM

Yeah. One of the reports mentioned that resistors exist that work at 500C, but existing capacitors don't, really.

Posted by: tasp Jul 17 2009, 03:00 AM

I think you need a capacitor to make a radio. And just making a high temp cap would not be sufficient, the device would need to maintain precise electrical characteristics over an extreme temperature range. All the parts would be subject to thermal noise effects, particularly amplifiers and digital circuits, and this might be another big problem.

Seems like the mining and drilling industry might have need of devices that would work in this regime. Maybe smelters too. Might be some incentive here to generate some useful spin off devices.

Posted by: siravan Jul 17 2009, 03:16 AM

Not exactly, temperature on the surface of Venus has a rather narrow range. In fact, the temperature difference between day and night sides is small. You need an electronic system which works in 450-500 C. It does not need to work in lower temperatures. Presumably, the cruise stage and the EDL stage can use separate, "traditional", microelectronic systems.

Posted by: Paolo Jul 17 2009, 05:46 AM

Conference on Venera-D (sorry, link in Russian only)
http://www.laspace.ru/rus/news.php#302

Posted by: stevesliva Jul 17 2009, 03:37 PM

I know. You and I are viewing this pretty similarly-- there's a whole 70 years of progress in electronics, discrete, IC, passives, packaging, boards, etc etc that needs to be reinvented for operation above 300C, which is a spec likely driven by automotive applications. Major skepticism. I think the only solution you could rely on in the near term is to throw it over to the mechanical and thermal engineers to make a colder box. The irony is that that's my take as knowing the EE side of things. I'm sure the mechanical engineers don't exactly find it easy, either... but at least there is more precedent for mechanical engineering in extreme environments.

Posted by: stevesliva Oct 1 2009, 04:45 AM

Just saw this article about SiC ICs being pushed to maturity by the hybrid and electric vehicle markets.
http://www.semiconductor.net/article/355220-SiC_Devices_Are_a_Long_Time_Coming.php

Posted by: Ulysses Oct 7 2009, 05:38 PM

Some news from the BBC:

http://news.bbc.co.uk/2/hi/science/nature/8294925.stm

Posted by: peter59 Oct 23 2009, 10:27 AM

Venus Climate Orbiter "PLANET-C" has new name AKATSUKI.
http://www.jaxa.jp/press/2009/10/20091023_akatsuki_e.html

You can send messages that will be printed in fine letters on an aluminum plate and placed aboard "AKATSUKI".
http://www.jaxa.jp/event/akatsuki/index_e.html

Posted by: Hungry4info Oct 23 2009, 01:03 PM

I thought they renamed their spacecraft after launch =o.

Posted by: centsworth_II Oct 23 2009, 05:50 PM

I guess that's when they will remove the quotation marks from "AKATSUKI".

Posted by: Paolo Oct 24 2009, 10:32 AM

Thanks to the "exuberant" performance of the H-IIA launcher, preferred over the original M-V, Japan will launch two additional payloads in solar orbit in addition to the VCO: the http://www.jspec.jaxa.jp/e/activity/ikaros.html and the http://unitec-1.cc.u-tokai.ac.jp/en/news_en

Posted by: Paolo Nov 26 2009, 07:44 PM

A few updates on Venera D from the Lavochkin site (in Russian) http://www.laspace.ru/rus/news.php#325

Posted by: punkboi Mar 4 2010, 10:17 PM

Akatsuki (and IKAROS solar sail) launch date set:

6:44:14 a.m. on May 18 (Japan time) / 5:44:14 p.m. EDT on May 17

http://www.jaxa.jp/countdown/f17/index_e.html

Posted by: Paolo Sep 28 2010, 09:15 PM

There is a nice article on SAGE in Air & Space http://www.airspacemag.com/space-exploration/Forbidden-Planet.html
no matter which mission is selected, the next New Frontiers selection will be an interesting one

Posted by: colin_wilson Nov 1 2011, 01:03 PM

Updates on the Russian Venera-D mission:

There is now a webpage (in Russian) : http://www.venera-d.cosmos.ru
An English version of the website may appear soon, but in the meantime one of several internet-based translation tools can be used.
This website still shows an original mission conception, which included a lower cloud balloon as well as a second upper cloud balloon, as well as a lander and orbiter.

A more recent presentation shows that the mission architecture has been simplified, and now consists of an orbiter, a sub-satellite, and a lander but no balloons.
http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-1334.pdf

Posted by: tedstryk Nov 1 2011, 06:52 PM

I recently did a write-up on it. http://planetary.org/blog/article/00003210/

Posted by: B Bernatchez Dec 31 2011, 02:15 AM

The article mentions that the operational life will be about 3 hours, which is the battery life. With a better power source, could this lander survive for longer? In other words, have there been sufficient advances in materials science that would allow a lander to survive, say, a week?, a month?

Posted by: vjkane Dec 31 2011, 05:56 AM

There have been various suggestions for a nuclear powered lander that would essentially operate an air conditioner to cool the critical electronics. Given the half life of Pu238, the life on the surface could be long. However, I don't think that the technologies are very far along in development. None of the Venus concepts studied by the Decadal Survey, for example, were long-lived landers.

Posted by: ncc1701d Sep 20 2012, 10:38 PM

How long until the technology from TanDEM-X and TerraSAR-X is used to map venus? I assume the technology would work there?
reference story blog here:
http://planetary.org/blogs/emily-lakdawalla/2011/2881.html

Posted by: machi Sep 21 2012, 04:43 PM

Missions for high resolution (1-10 meters) radar imaging of the Venusian surface were proposed by multiple teams. Most active today are teams from Israel (http://www.ursi.org/proceedings/procGA11/ursi/J05-1.pdf mission with possible NASA cooperation) and http://www.asianscientist.com/topnews/isro-indian-mission-to-planet-venus-2012/.

Posted by: JRehling Sep 21 2012, 06:20 PM

To reply to the lander posts from December, I'm linking to this thread from even further back:

http://www.unmannedspaceflight.com/index.php?showtopic=4544&mode=threaded&pid=98136

In a nutshell, the problem for Venus landers is that innovative approaches to the heat require technological advances, which add to the mission cost and in a competitive environment, put any Venus surface selection at a disadvantage relative to the competitors. If the technology development were distributed over multiple missions that could make use of high-temperature endurance, that would be more favorable. We could have a dynamic where Venus surface missions keep losing Discovery / New Frontiers competitions ad nauseam, lacking the added support of technology for a superior science return. Note that the United States still has never launched a mission to Venus's surface (the one Pioneer probe which survived a short time withstanding).

In contrast, Venus holds advantages over most other destinations for orbital missions.

Posted by: vjkane Sep 22 2012, 12:47 AM

I wrote a blog entry on one of the Venus Discovery proposals, http://futureplanets.blogspot.com/2009/11/proposed-discovery-venus-radar-mission.html. As with all the other Venus Discovery proposals in the latest competition, it was not selected as a finalist.

In addition to the MuSAR proposal linked to above, the European science community is putting together a proposal that would use radar to monitor surface height changes as a measurement of geologic processes.

The track record for Venus mission proposals of any type -- orbital, entry probe, lander -- has been so poor that I wonder if competitive missions can be fit within the smaller cost-capped programs. So much may have been done that the cheap missions can't do exciting enough science to be selected and the missions that would be scientifically competitive bust the cost caps.

Posted by: dtolman Mar 13 2013, 02:24 PM

Haven't seen it mentioned here but the Venera D mission appears to be on long-term hold according to the most recent reports.

Damn shame, as Venus has had virtually no surface exploration, and this is planned to include a lander and do surveys for future landing missions.

MOD NOTE: Moved posts about high-temp electronics for surface missions to its own topic http://www.unmannedspaceflight.com/index.php?showtopic=7628&hl=.

Posted by: colin_wilson Jul 30 2013, 10:52 AM

Hi -

You may be interested to see this paper describing why ESA should spend €1bn to go back to Venus (and how they should spend it!).
I submitted this to ESA in response to a call for Science Themes for their next Large (€1bn) mission.
Don't hold your breath waiting, though; This is for launch opportunities in 2025-2035.

The paper can be downloaded here:
http://www.atm.ox.ac.uk/user/wilson/Venus_ESA_L2L3_whitepaper_Wilson_2013.pdf

-Colin Wilson

Posted by: Phil Stooke Jul 30 2013, 01:36 PM

Thanks for posting that.

Phil

Posted by: TheAnt Aug 26 2013, 05:42 PM

Venus landsailing rover, a proposal and study of the concept.

http://www.nasa.gov/directorates/spacetech/niac/2012_phase_I_fellows_landis.html

http://www.nasa.gov/pdf/745590main_Landis-2013-SpringSympPresentation.pdf

Posted by: Explorer1 Aug 27 2013, 02:57 AM

Now that is an original idea, and it actually looks plausible, and the idea of control from orbit to circumvent the heat problem for electronics is especially ingenious. The 'Zephyr' deployment looks highly complex though; all those moving parts, and a parachute that could get tangled up...

Posted by: Chmee Aug 27 2013, 03:32 PM

Yes, very original idea! However, having both high temperature electronics and the wind-sailing in the same probe seems too risky and very complex.. Instead, doing a 'proof of concept' stationary Venus lander with just the solar cells and high temp electronics, sounds like a good first step. In the same way that Mars Pathfinder tested new landing and rover concepts on Mars (i.e. a "Venus Pathfinder").

Posted by: vjkane Aug 29 2013, 06:07 AM

Chmee - Good point. I also didn't see much about instruments in the presentation. All well and nice to be able to sail around the surface with the brains in orbit, but are their designs for cameras, spectrometers, etc, that can operate at Venus ambient?

Posted by: Explorer1 Aug 29 2013, 07:11 AM

Well the Venera missions did much of the pioneering work in that regard. Landing site matters too: the Venusian Everest is the best place in terms of both engineering and scientific interest (figuring out conclusively what the 'snow' on Maxwell is).
I'd also settle for a descent cam, Huygens style...

Posted by: 0101Morpheus Dec 9 2013, 06:06 PM

Here is a recent article on how a Venus mission can help us solve a lunar mystery. The reasons to send something there just keep piling up.

http://science.time.com/2013/12/04/new-take-on-an-ancient-mystery-how-earth-got-its-moon/

Posted by: Paolo Dec 9 2013, 06:57 PM

here you can read the article by Robin Canup. I always prefer reading the "first generation" articles
http://www.nature.com/news/planetary-science-lunar-conspiracies-1.14270

Posted by: JRehling Jan 5 2015, 07:44 PM

In the past two years, some various news and non-news that seems relevant to Venus exploration (and non-exploration!):

Plans by Russia and India for future Venus missions have been pushed back or gone mute. But in the meantime, India and China have had successes with missions to the Moon and Mars, which has some bearing on the capability of the world's developing space programs to be able to explore Venus.

Venus Express has done some great science from the orbital view looking down in IR/UV. Many of the major goals that remain, as described by VEXAG, focus on the lower atmosphere and surface. I think recent successes by India, China, and Japan show that some great Venus missions could be performed by these programs if they focused their attention there. In particular:

1) Sensitive in situ measurements of composition in the lower atmosphere: The best data we have came between 1978 and 1984, now over 30 years old. Huygens, using instruments of a vintage about half that age produced atmospheric composition measurements a few times more precise than we have for Venus. If that level of sensitivity could be improved upon for Venus, then calculations of isotope ratios would be highly improved from what we have now, and that would have a lot of bearing on our understanding of Venus's crustal/atmospheric evolution. That, in turn, has a bearing on understanding how Earth, Mars, and extrasolar terrestrial planets have evolved.

2) There has never been descent imaging performed at Venus. Even a probe lacking the ability to survive Venus's surface heat could return imagery from altitude that is vastly superior to the resolution of Magellan radar. A well-placed landing site could image two or more surface units as Huygens did on Titan, using existing maps to target the descent site(s), which could be chosen independently of the atmospheric goals. Two probes could potentially image four surface units from altitude.

2b) Older probes showed that short-term survival at the surface is not unattainable, so descent imagining could potentially turn into surface panoramas.

3) A radar mapper superior to Magellan is another worthy goal, and is yet another way to do great science without dealing with the surface heat.

It's hard to operate on the surface of Venus, but it's not hard to cruise to Venus and descend into its atmosphere. So far, China and India have prioritized Mars ahead of Venus in their space exploration plans. I think their interests might be served better by staking out some territory that the more active space programs have ignored, and Venus is a pretty big swath of territory not so far away.

Posted by: vjkane Jan 6 2015, 06:01 AM

I think that we can expect several NASA Discovery and ESA M-class proposals for Venus in the coming months. The proposals seem to split between geology orbiters (radar and thermal spectrometers) and atmospheric probes or balloons. The numerous Earth science radar missions appear to have matured the technology to the point where Discovery or M-class missions are possible. I'm less familiar with probe and balloon technologies, but the teams proposing them are experienced and credible.

There are so many good ideas for Discovery and M-class proposals that it is hard to pick a favorite target. The Venus community has waited so long for a mission, though, that I will admit that a Venus mission seems due.

Posted by: JRehling Jan 12 2015, 08:39 PM

Another look at the quality of Venus data:

The isotope ratio of 14N/15N on Titan is known to a degree of accuracy 100 times that of the same ratio for Venus.

I can't suss out how much of this is due to differences in the task (Titan's atmosphere is nearly all nitrogen) and how much to the fact that the relevant instruments performing the measurements were about 15 years older in the case of Venus. However, there have to be some gains to be had by flying a vintage 2015 instrument to Venus in order to update the data from 1983 instruments.

Posted by: katodomo Jan 12 2015, 09:03 PM

Realistically, going by the recommendations from the committee for the ESA L2/L3 selection, the thing that has a chance of getting through (and then a good chance for selection) is a moderately cheap high-resolution radar mission, something that builds on, renews and improves the Magellan data. Preferably with a limited-time frame of operations, nothing multi-year, and preferably with a proven, technologically mature bus.

Posted by: Holder of the Two Leashes Jan 12 2015, 11:45 PM

Given the slow rotation of Venus, that is asking to give up a lot. Creating views from different angles to give you 3D topography are automatically going to be more than one year of mission time if you want to cover a substantial part of the planet. Using MESSENGER as a reference, I don't expect anyone to vote against a Venus proposal for which a four or five year lifetime could be expected. At least not on that basis alone (i.e. they prefer some other mission entirely). Expecially given how fast it would get there.

Posted by: vjkane Jan 13 2015, 05:05 AM

Since Magellan, synthetic aperture radar (SAR) has advanced a great deal, and a number of Earth observing satellites now use it. This gives a solid technology base for a Venus radar mission that significantly improves on Magellan's resolution. The general wisdom is that such a mission could be done within the price cap of either a NASA Discovery or an ESA M-class mission. The various proposals vary in how much of the planet would be re-imaged and the focus of the scientific questions (which relates to what gets re-imaged). Most of the proposals also include a thermal emission spectrometer for low resolution (~50 km) composition studies and radio tracking for improved gravity studies. Some proposals also have some other instruments. (Discovery proposals seem to have fewer instruments, probably because the proposers have to pay for the instruments; M-class missions seem to have more, probably because instruments are paid for outside of ESA's budget.)

Posted by: Phil Stooke Jan 13 2015, 02:16 PM

Better topography is high on many lists for desired Venus data sets. Magellan altimetry is extremely poor relative to MOLA and LOLA data - a result of having to use radar instead of lasers. There is stereo SAR for parts of Venus, but as yet no integrated global topo dataset. Radar interferometry is touted as a way to get high resolution topography and it would be highly desirable. That plus targeted partial SAR coverage at very high resolution would make a fantastic difference to our understanding of Venus.

But so would almost everything else that is being proposed! Personally, I would like to see surface imaging with MER Pancam-type coverage and resolution instead of the partial strip coverage from Venera cameras, for a few different terrain types.

Phil

Posted by: stevesliva Jul 9 2015, 09:59 PM

Saw this today in AWST:
http://aviationweek.com/space/semibouyant-aircraft-could-explore-venus-s-upper-atmosphere

It is a pie-in-the-sky from Northrup Grumman... a big inflatable lifting-body pie.

Seems there is an older writeup of it with some nice images here:
http://motherboard.vice.com/read/the-inflatable-plane-that-would-float-like-a-leaf-through-venuss-atmosphere

It's called VAMP, and the latter link points to a Jan 2013 presentation:
http://www.lpi.usra.edu/vexag/meetings/STIM/presentations/Polidan_VAMP%20for%20STIM%20Meeting%20Jan%202013%20-%20Final%20Approved.pdf

Posted by: JRehling Oct 2 2015, 04:07 PM

The next slate of Discovery mission candidates has 2 Venus missions in the 5 finalists (the other 3 are all aimed at asteroids). NASA has, remarkably, only sent two missions to Venus since 1967, and none since 1989. The drought may be over.

VERITAS would be an orbiter that would use radar and radio science to study the surface of Venus, returning an excellent map of the entire surface.

DAVINCI would be an entry probe that would give us precise measurements of atmospheric composition and descent imaging.

I'd love it if either of these made the selection, and if both of them could fly eventually. (The asteroid missions aren't bad, either.) All of our Venus knowledge comes from instruments that are now 25-30 years out of date, and this leads to significant deficits in our knowledge of how Venus – and therefore, terrestrial planets in general – evolved. As we start to get curious about Earth-sized planets orbiting Sun-like stars elsewhere, it's a little crazy that we have one that can be reached with just a 3-month cruise and we've decided to ignore it.

Posted by: ZLD Oct 2 2015, 05:43 PM

Won't probably happen due to the constraints of the program but there would be some cost savings in sending both together. That would be my preference.

Posted by: ngunn Oct 2 2015, 06:25 PM

I found a little more about DAVINCI on the AAAS website:

DAVINCI would drop a spherical metal ball through the Venusian atmosphere. Studded with sensors, the probe would relay its measurements to Earth via the carrier spacecraft. It would also make the first images of Venus’ surface since the Soviet Venera landers of the 1970s. Glaze says her team will aim DAVINCI at Venus’ “tesserae,” regions of crumpled terrain that are thought to be the remnants of continents. “They’re really mysterious -- we don’t know what they are,” she says. “We’ll be taking pictures of these for the first time.”

Posted by: elakdawalla Oct 2 2015, 08:18 PM

I have the following tidbit of additional information from Lori Glaze:

And this from David Grinspoon:

Posted by: scalbers Oct 2 2015, 09:41 PM

As a comparison I wonder how VERITAS radar would compare with Magellan and related maps of the surface?

And would DAVINCI imagery be comparable to what Huygens saw on Titan?

Posted by: JRehling Oct 2 2015, 10:23 PM

I think we can expect roughly a 4x improvement in radar resolution vs. that of Magellan, but I'm just estimating that from Cassini and other proposed Venus missions that sit hazily in my memory.

Huygens delivered about 3-4x the precision of Pioneer Venus and the Venera missions in determining atmospheric composition. This could be a radical improvement in scientific understanding, because determining the ratio of noble gas isotopes depends upon accuracy better than the abundance of the rarest isotope you care about. The best Venus measurements were made with tech that is already 30-40 years old!

I don't know how to estimate the quality and value of descent imaging. Venus has a heck of a lot more light reaching the surface than Titan does, but the devil's in the details as to what you see when you look down on Venus: It's never been done before. If the whole area has the same albedo, then it might look pretty bland from above. It's up to Venus to deliver something to look at.

I don't know if DAVINCI would make it to the surface and give us a (partial) panorama from there. Usually, things that have dropped into Venus' atmosphere have made it to the ground, but the cameras may not be side-looking (?).

Posted by: scalbers Oct 2 2015, 10:34 PM

If this is a spherical probe we could hope for full 360 degree (spherical) imaging? This is becoming more popular in some terrestrial cameras on the market.

Posted by: machi Oct 3 2015, 10:58 AM

Resolution in case of imaging at least 4× better (30m vs 120m globally) and topography at least 40× better horizontally (250m vs 10-30km) and 6× vertically (+/-5m vs +/-31.5m).
It means better topographic map of Venus than we have now for Mars!

Posted by: Paolo Oct 3 2015, 01:20 PM

why so long? it takes much less than 19 months to get to Venus using a conventional Hohmann orbit

Posted by: Explorer1 Oct 3 2015, 03:31 PM

Maybe it won't be a conventional transfer? Perhaps solar electric propulsion or an Earth gravity assist?

Posted by: vjkane Oct 3 2015, 04:04 PM

A goal of the mission is to descend over one of the tesserae. They may need a transfer orbit that provides a specific set of solar illumination and visibility from Earth tracking stations over the entry point.

Posted by: HSchirmer Oct 3 2015, 06:24 PM

Ok, so I just looked over the recent posts about a Venus-blimp-lifting-body proposal. It occured to me that Venus might be a good topic for wild ideas -

The surface temperatures and pressures on Venus are brutal, it is more like an ocean than an atmosphere. So, what if we treat exploration of Venus more like bathymetry, with a bundle of instruments on a tether. Drop it down, get the data, pull it back up before it melts.

So, here's one. I just read about New York skyscrapers saving power by making ice at night to store cooling power. Occurred to me that something similar might work well on a Venus blimp/flying wing. Solar powered refrigeration units create dry ice. Vent the blimp, drift down to the surface, get your measurements while CO2 evaporation cools the probe. Have the CO2 fill a couple of high temp weather balloons to lift you back up.

Posted by: ZLD Oct 3 2015, 08:12 PM

I'd be highly interested to see this seriously explored but I would expect the miniaturization, low power requirements and low mass requirements would prevent this type of mission at this time. However, with enough money, anything is possible in a short time.

Posted by: ngunn Oct 3 2015, 08:28 PM

I like the idea of using a phase change to drive raising and lowering through the Venusian atmosphere. Water would be another possible material for this purpose. Perhaps we are in for a new age of steam . . I think we can leave constraints like cost and mass at the door and just think about ideas, as long as they don't require fantasy science. The best ways of exploring Venus will be unique to that world. If the idea's good enough it will be paid for, and hefted. It's time for Venus!

Posted by: HSchirmer Oct 4 2015, 01:26 AM

Ok, following up on earlier idea about a Venus probe, a sort of stratospheric diving bell.

If you happen to be 50 kilometers above Venus, it appears to be rather comfortable.
Standard earth pressure, standard earth temperatures, a bit of sulfuric acid rain, but tolerable.

Recent suggestion include a solar powered flying-wing-blimp,

and brain-ship loitering in the cool air, controlling a dumb but heat tolerant rover by radio...

I figure its' about time to think about what other ideas might work?

Lets consider "off the shelf" technology- specifically http://foxtrotalpha.jalopnik.com/how-dumb-cluster-bombs-got-heinously-smart-1673486769. We now have cluster bomblets that use rotating laser and infrared scanners to survey the battlefield, identify targets, prioritize targets, and then navigate there.

I would suggest a similar layout, but to deliver science, not semtex.

Posted by: vjkane Oct 4 2015, 05:07 AM

There's a http://futureplanets.blogspot.com/2015/10/finalists-for-next-nasa-discovery.htmlt with additional information on the Discovery finalists. You can follow links for more detail for several of the proposals.

Posted by: Paolo Oct 5 2015, 07:39 AM

You may be right. We will probably know more as more info on the mission is released.
BTW, I remember that Magellan too took 15 months and one and half orbit around the Sun to arrive at Venus. In that case, however, the orbit design was due to NASA opting not to launch two back-to-back Shuttle+IUS missions (Magellan and Galileo) on the same Venus launch window.

Posted by: JRehling Oct 5 2015, 04:06 PM

It's curious that the landing sites already visited and photographed (Veneras 9, 10, 13, and 14) were in each case close to tessera or highland units, which seems very unlikely given how much of the planet is wide-open flat planitia. They are also in a very narrow band of longitudes due to the combination of the unexplained synchrony between Venus' revolution and the Earth-Venus synodic periods; the re-use of minimum-energy trajectories in every case; and, the desire to have a day-lit landing site. The aforementioned Veneras as well as the Pioneer Day and Large probes all landed within about 30° of longitude. If one of those variables changes (namely, length of cruise), then a totally different band of longitudes will be selected, potentially a wider one if Venus is gibbous rather than crescent at arrival.

Tesserae are pretty widely distributed. Most 60° bands of longitude would give you 1 or more tesserae landing sites to choose from.

Posted by: HSchirmer Oct 5 2015, 04:52 PM

Well, it might only be necessary for raising.
Just occurred to me, after considering the spinning cluster bombs, that probes shaped like maple spinners could make a controlled descent.

If the probes had a camera pointed off-axis, you could naturally build up a spiral image, getting higher and higher resolution as you descend.

Seems that Venus has enough atmospheric diffraction that solar panels on the top and bottom of a wing can provide almost equal power.
So, perhaps a bunch of cube-sats tucked into a maple spinner enclosure, floating at 50km and using solar power to replenish a dry-ice cooling system, then fluttering down to the surface, use CO2 gas to inflate and lift back to 50 km, start all over again.

The other idea, that literally floated in, is to copy orb-spiders. When spiders hatch, they spin a thread, catch a breeze and fly away.
Even heavier adult spiders http://www.americanarachnology.org/JoA_free/JoA_v29_n1/arac_29_01_0114.pdf although they actually create a 2d "sail" rather than a 1d string.

So, anybody have ballpark energy requirements for probes floating in Venus's CO2 atmosphere, making dry ice to cool a lander, or fabricating polycarbonate sails?

Posted by: JRehling Oct 5 2015, 06:12 PM

Great writeup, Van, as always!

Posted by: xflare Jan 11 2017, 08:11 AM

Well, the only hope for a Venus mission in the next decades rests with the Venus in situ Explorer now

Posted by: vjkane Jan 11 2017, 05:05 PM

I'm listening to Jim Green's program update at SBAG. He has now said several times that the asteroid missions were selected because they were "most technically ready" and "best fit into a cost capped program".

If you look at Lucy and Psyche, the spacecraft are straightforward, the instruments are all near copies of existing instruments, and the data return rates are likely pretty modest. The latter is one of the key drivers of spacecraft cost.

DAVINCI had the challenge of having a carrier probe (simple in itself, but another element), a high pressure vessel, and expensive composition instruments that had to be modified to work with high pressure, high temperature gasses.

VERITAS was using a modification of radar systems used at Earth, but I don't know if any modifications were required. The biggest challenge, I suspect, was the data return rate which would have driven the cost and complexity of the entire spacecraft system. (Ralph Lorenz published a great paper on how data rate is the driver of planetary mission costs.)

Following the cost overruns of the last decade following the selection of more ambitious missions, NASA's managers appear to have become more conservative. While surprises happen (InSight, for example), in general this has worked.

Posted by: vjkane Jan 11 2017, 05:09 PM

The Huygens probe used spin to build up images. I can't remember if the spin was created by the parachute design or vanes on the probe.

Posted by: vjkane Jan 11 2017, 05:14 PM

The European community has united behind the EnVision Venus mapping mission for the M5 (fifth medium) class mission. It is similar to VERITAS with the biggest difference being the addition for EnVision of a subsurface radar instrument. We will know if it made the list of finalists mid year this year. Launch target is the very late 2020s.

There's also a joint Russia-US Venera-D mission in early discussion that would include an orbiter (I think without a radar unit) and an atmospheric probe/lander. However, the Russian space program is strapped for cash and has an ambitious lunar program in the queue ahead of any Venus mission.

There's also been vague (in the public press) talk about other space agencies such as China doing some kind of Venus mission.

Posted by: rlorenz Jan 13 2017, 02:33 PM

Such winged seeds are called 'samaras', and have been proposed for planetary atmospheric sensing, but typically would give you higher angular rates than you would want for imaging. (They are discussed at some length, as well as the spin vanes on Huygens, spinning parachutes, rifled bullets etc in my book "Spinning Flight : Dynamics of Frisbees, Samaras, Boomerangs and Skipping Stones"

Achieving slow descent on Venus is not usually a problem with conventional vehicles, however, since the atmosphere is so dense.

Small vehicles (like the 'cubesat') do not work well in the deep Venus atmosphere as they would warm up very quickly - active cooling doesnt scale down efficiently.

Posted by: JRehling Jan 10 2018, 05:37 AM

Latest Venus mission news:

There was a selection of candidates for the next New Frontiers mission, and for the many-th Discovery/NF selection opportunity, Venus was not selected.

However, a Venusian silver lining: The VICI mission program led by Lori Glaze was one of two non-finalists to receive funding for future mission development.

Among the many Venus proposals in recent years, VICI is distinguished by its plan to send two landers to two different areas of tessera terrain. This is likely the oldest terrain on Venus, and includes the possibility of landforms that were created before Venus had its current climate, dangling the possibility of evidence of a cooler, perhaps even wet, past.

For now, Venus isn't at the front of the queue for New Frontiers missions, but that's one piece of encouraging news.

If VICI or another comparable mission flies in the next few NF missions, it could become the first designated U.S. surface science lander on Venus, only sixty years after the first Soviet lander arrived!

Posted by: hendric Feb 13 2018, 07:24 PM

Interesting article about future missions and capabilities.

https://www.sciencenews.org/article/what-will-it-take-go-venus?tgt=nr

Posted by: vjkane May 7 2018, 03:35 PM

The EnVision Venus mapping mission was just selected as a finalist for ESA's M5 call (flight in late 2020s or early 2030s?)

http://sci.esa.int/cosmic-vision/60257-esa-selects-three-new-mission-concepts-for-study/

http://www.envisionvenus.net/index.php

Posted by: JRehling May 27 2018, 06:37 PM

Venus exploration is at an interesting crossroads, because it now has a hand in three different competitions, and could win big if it is selected in two of those, or be neglected yet again if it is selected in zero.

EnVision plus VICI or any of the Discovery options with a lander, for example, would do a great job of revolutionizing the state of Venus science, undoubtedly leading to quite different possibilities for any subsequent mission to advance things further. In the best case, we could be at that status in the mid 2030s. In the worst case, we could reach the 100th anniversary of Mariner 2 with the last U.S. mission to Venus being Magellan and the last lander being Venera 14.

Posted by: vjkane May 28 2018, 03:11 PM

Right now, Venus is in just one competition I'm aware of: EnVision in ESA's M5 competition (launch target appears to be early 2030s). I suspect that there will be proposals in the next Discovery competition, beginning next year if I recall with flight in mid-2020s.

Posted by: JRehling Jun 3 2018, 06:01 PM

That's right, and more precisely, that is the only competition in which a Venus mission is alive for this cycle. I was referring to the ongoing presence of Venus missions in the Discovery and New Frontiers competitions which seems likely to continue until the alternatives are exhausted. The Venus concept VICI also has technology development funding (for the laser spectrometer, such as currently working on Mars) in hand from New Frontiers, which isn't a mission, but is a small start towards one. I'm not sure if that technology development could be used to strengthen the DAVINCI concept, like VICI led by PI Lori Glaze, in upcoming Discovery competitions. DAVINCI was more of a descent atmospheric probe with some surface imaging and a laser spectrometer whose goals only mention the atmosphere, not the surface, although the similarity to the Mars Curiosity instrument is mentioned. I'm curious if the atmosphere-only limitation on DAVINCI's laser spectrometer was due to expectations that it would fail before reaching the surface. If so, the technology development funding for a surface laser spectrometer on VICI could make DAVINCI a significantly more capable mission than in the last competition. One could imagine a very busy surface science mission of an hour or two while it composition-zapped nearby rocks.

It seems like Venus could win the second, third, or fourth -next New Frontiers mission competition (after Dragonfly or CAESAR), and/or the next Discovery mission competition (after the two asteroid missions fly). Nothing is guaranteed, but the competition would seem to be getting thinner every time Venus loses.

Posted by: vjkane Jun 4 2018, 04:37 PM

From other readings on LIBS/Raman spectroscopy on Venus' surface, there are challenges to both the transmission of the pulses and interpreting the resulting spectra under the very dense atmosphere. I don't think that there were any questions about its survival to arrive on the surface (and it wouldn't operated except on the surface).

An atmospheric probe (VICI - Discovery) and an orbiting radar/thermal spectral mapping orbiter (VOX - New Frontiers; VERITAS - Discovery) were judged at Category 1 (fully selectable by meeting all scientific and programmatic requirements) in the last Discovery and New Frontiers competitions. (Despite being Cat 1, VOX was not selected as a finalist, which was noted by the Venus community.) I would expect that both will be re-proposed for the next Discovery selection which will begin next year.

Between them, VICI and VOX/VERITAS would meet the high priority scientific goals laid out by the last Decadal Survey for Venus. (The VOX team apparently successfully argued that the surface study goals could be met by an orbiter, replacing the previous assumption that a lander was required.)

Interestingly, the time period for selecting the M5 mission (for which EnVision is a competitor) and the next Discovery mission will be similar. I hope that the two agencies don't select a Venus orbiter in the hopes that the other will.

Posted by: vjkane Jun 4 2018, 05:09 PM

Venus Landed Platform Working Group

NASA has convened a Venus Landed Platform Working Group to assess high priority science investigations that are needed on the surface of Venus. Topic areas include Venus surface geology and geochemistry, atmospheric chemistry and dynamics, interior processes, and surface-atmosphere interactions. This includes investigations that may be enabled by new technology approaches, such as extended duration landers via active cooling or high temperature electronics, or using surface mobility. Individuals who would like to suggest important science investigations should please send a short description of the science question being addressed, the measurements required to answer the science question, and key technical requirements such as measurement duration or mobility requirements. Please send this input to the following individuals:

Martha Gilmore, mgilmore@wesleyan.edu
Natasha Johnson, natasha.m. johnson@nasa.gov
Walter Kiefer, kiefer@lpi.usra.edu
Jonathan Sauder, jonathan.sauder@jpl.nasa.gov

The Working Group’s first meeting begins on June 19.

Posted by: JRehling Feb 12 2019, 07:33 PM

This has been online for months now, and I'm just taking a look.

https://link.springer.com/article/10.1007/s11214-018-0528-z

Very exciting plans… but of all the proposed missions and architectures, not many are on a solid path towards implementation. The Indian orbiter seems likely. Otherwise, we have Venus as being no better than second in line for a New Frontiers mission and the Envision orbiter (which would be a grand all-purposes Venus orbiter) one of three candidates for a future ESA mission.

Posted by: vjkane Feb 14 2019, 08:07 PM

The Indian orbiter will carry a number of instruments, but it appears to have some severe limitations on payload mass and data rates.

The proposed ESA EnVision radar and infrared mapping mission wouldn't launch until the early 2030s if selected. It is facing severe cost and mass limitations. NASA is investigating whether it could provide the major radar mapping instrument.

The Venera-D joint Russian (lead) & US lander and orbiter could fly in the mid-2020s, but Russia is strapped for cash.

That leaves the two Discovery missions to be selected (as I remember) in 2021 for flight in the mid and late 2020s as the only other opportunity.

Posted by: JRehling Feb 15 2019, 06:53 AM

It's interesting to me that EnVision and VOX both propose the same instrument to probe emissivity in the IR, as does the Discovery proposal VERITAS. I think that Venus Express' PFS instrument would have returned some of the same value, except that it failed and returned no data at all (the Wikipedia page erroneously reports that it did, probably a hasty editor converting original plans into the past tense after the mission ended). In a nutshell, this is similar, for Venus, to what VIMS on Cassini accomplished at Titan, making use of haze-penetrating bands to observe the surface. It would be great to have an orbiter in a low circular orbit provide this or a resolution of radar superior to that of Magellan or, as both EnVision and VOX propose, both.

It seems not impossible that VOX or another Venus mission could be the second or third next New Frontiers mission, which looks like the 2030s, as would be EnVision.

The Discovery missions have seemingly chosen every conceivable non-Venus mission that anyone can propose with Venus almost inevitably getting to the front of the queue eventually. Proposals for the next Discovery missions are due at the end of this month. If VERITAS were chosen, that could likely knock EnVision and VOX down in value, and make VICI a candidate for a future New Frontiers mission in the 2030s.

Posted by: hendric Mar 18 2019, 03:18 PM

Our company recently hosted Dr Jean Anne Incorvia from the UT Integrated Nano Computing Lab for a lecture on Magnetic RAMs. Of course, I asked a bunch of space-focused questions. She said they are very robust at high temperatures (tested up to 250C) and radiation environments, and are well suited to space operations. The transistor part of the structure is vulnerable to damage, but the memory element itself is very tough. Endurance testing is over 10^15 modify cycles. Time to rewrite a bit is on the order of 1-10ns. I also brought up Silicon Carbide as the semiconductor substrate for the ferro structures, but nobody is looking at that. (Potential opportunity there!) With Curie temps in the 1000C range, I am hopeful we have a perfect memory for an upcoming Venus lander/rover!

http://www.utinclab.com/

Posted by: stevesliva Mar 18 2019, 05:50 PM

You were right to ask about SiC. The MRAM junction might be high temp tolerant, but the associated FETs are not.

MRAM does have its own sort of soft error rate (bits flipping randomly, not necessarily radiation induced.) So I would wonder if that rate increases with temperature. MRAM, though, seemingly has a lot less complex circuitry to fail than Flash does. Density is years behind, though. The stuff they do with Flash now is insaaaane. Very far removed from zeroes and ones.

Posted by: hendric Mar 18 2019, 06:19 PM

Probably some quantum tunnel magic I suppose. The Dr mentioned that as the temperature rises your speed would increase since it is easier to flip bits but your error margin would decrease. Dealing with bad bits is NAND bread&butter though so it should be easy enough to mitigate.

Yeah modern flash memory now is MLC, basically instead of just reading a straight 0 or 1, it reads mid-level voltage levels and translates that into 000 001 010 011 etc. That makes it extremely susceptible to disturbs (reading bits at X,Y has a chance of messing up their neighbors), lowers the lifetime of the cell when turned off as the electrons slowly drain, and much more vulnerable to radiation induced damage.

MRAM is still fairly young tech for semiconductors (original Space Shuttle used ferrite cores, so the concept has been around a long time!), but based on her talk there is plenty of run room and the potential for very high densities.

Posted by: vjkane Mar 22 2019, 12:35 AM

A German lab has been developing an IR emissivity instrument for over a decade or so. They have done extensive work on the instrument development and on interpreting the multispectral results in terms of composition. This instrument has been included on every post-Venus Express mission that I know of except possible the planned Indian mission.

Posted by: vjkane Mar 24 2019, 02:56 PM

Here's a link to an LPSC 2019 abstract:

http://www.hou.usra.edu/meetings/lpsc2019/pdf/2046.pdf

Posted by: JRehling Mar 24 2019, 04:19 PM

A nice summary! I've seen other write-ups of the specs and it's a phenomenal instrument design for a specific case of interest.

Now the pity would be if the Indian mission is the only planned Venus orbiter that doesn't include it and ends up being the first to fly, which it could be by a margin of years. If we have to wait ~15 years to get this data back, it will be a pity when it could easily be done within 4 years if Venus were a higher priority.

Posted by: Steve5304 Apr 3 2019, 03:33 AM

Just read the Russians gave agreen light and will send a new lander before 2023. Hoping to use some experimental tech to allow the probe to operate in extreme temperatures. Nasa is interested in helping develop this technology

I know roscosmos says alot and doesnt follow through. But Venus is definitely something they are capable of.

Posted by: Paolo Apr 3 2019, 05:26 AM

or at least they were capable of. I doubt that almost 35 years after the most recent successful Russian planetary mission they are retaining any of the know how

Posted by: bobik Apr 3 2019, 08:35 AM

The https://www.lpi.usra.edu/vexag/reports/Venera-DPhaseIIFinalReport.pdf calls for a https://www.lpi.usra.edu/vexag/reports/Venera-DPhaseIIFinalReport.pdf#page=145.

Posted by: Steve5304 Apr 3 2019, 07:38 PM

thanks for that. Glad I can count on this place to be accurate.

Yahoo later corrected the article to 2026.



Man Russia needs a win so bad. The last somewhat successful interplanetary mission was....what ? ..Phobos II....somebody?

Posted by: Paolo Jun 5 2019, 04:41 PM

in today's Nature:
https://www.nature.com/articles/d41586-019-01730-5

Posted by: atomoid Jul 3 2019, 09:50 PM

Phobos2 though unfortunately not fully successful, did get some https://web.archive.org/web/20150717180620/http://www.strykfoto.org/phobos2.htm, yet it seems to be the most recent Russian exploration mission to at least make it beyond Earth orbit. The most recent success seems to be Vega which after a couple of as-yet unmatched firsts in deploying landers and balloons to Venus, continued another first visiting Halley in 1986 according to https://en.wikipedia.org/wiki/Timeline_of_space_exploration. After the breakup of the USSR, other than the Russian's fine and clockwork Soyuz activities and contribution to ISS, its unfortunately been crickets as far as exploration is concerned. It looks like Luna25 in 2021 is their next hope in a long line of false starts, found this article on http://www.thespacereview.com/article/3611/1

Posted by: atomoid Oct 24 2019, 11:41 PM

new https://www.wired.com/story/nasa-wants-to-send-a-probe-to-the-hellish-surface-of-venus/ on the LLISSE is interesting once you bat away all the adverts.
The 20cm cube is designed to stay operational for 60 days capturing day/night transition, but likely have no camera, is hoping to hitch a ride on Venera-D.
Also found an old https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180000692.pdf and another older? https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180004539.pdf mentioning a possible wind-powered battery option for demonstration in 2023. Wind speeds are so fast at altitude it https://www.sciencemag.org/news/2018/06/wind-hitting-venus-s-mountains-makes-planet-rotate-faster the planets rotation by 2 minutes per day, wind slows at the surface to apparently a few km/hr so seems workable, solar cells should be considerably less mass but im not sure what the https://www.hou.usra.edu/meetings/venusmodeling2017/pdf/8002.pdf though ive also heard due to high albedo Venus actually receives less energy at the surface than Mars does.. here's https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190001008.pdf.

Posted by: tanjent Nov 20 2019, 06:15 PM

https://www.space.com/possible-nasa-venus-flagship-mission.html

This article discusses the possibility of a flagship-class mission to Venus sometime after 2023.
One may argue that recent Venus proposals have failed because they are too cautious, so perhaps a multifaceted
approach on the scale of Cassini would stand a better chance of success.
Mentioned are multiple orbiters, long and short-term landers, and a balloon-based aerial platform with, (sic) a seismometer.
Despite its ambitious nature, the proposal strategy seeks to be cheap relative to other flagship-class contenders.
I guess that means we'll have to wait a few more decades for a sample return.
,

Posted by: JRehling Nov 21 2019, 04:05 AM

Interesting timing, given that three Discovery proposals aimed at Venus are now being evaluated with an announcement of selection for Step 1 targeted for January 2020, only weeks from now. Any of those three would satisfy the flagship aims partially, so the proposal of a flagship mission puts some (more) people/programs at cross purposes, and the community has to have a lot of overlap; there can't be very many people who would be investigators for the flagship mission who aren't involved with some of those Discovery proposals.

Orbital studies of the surface and orbital/descent studies of the atmosphere are both addressed by the Discovery proposals, in addition to the descent imaging of tessera terrain. The flagship mission includes a lot more in situ surface focus.

The timing feels off unless the people proposing the flagship mission have a strong sense that the Discovery proposals are all going to be rejected. Otherwise, the flagship goals could descope and focus with the satisfaction of some of those goals.

Posted by: tanjent Nov 21 2019, 10:26 AM

I don't recall any precedent for gathering together several discovery-scale proposals with the same destination and consolidating into a single flagship-scale mission. But there could be some efficiencies in launch, data return, shared infrastructure. Politically it would be difficult to persuade the individual would-be PI's to report to a single overall head, but I suppose they might be willing to settle for a piece of the action with high probability, in place of a low-probability shot at being the sole focus.

Anyway, I am just imagining that; the article mentions no such consolidation. It seems to describe a top-down effort by someone who wants to design the whole venture from scratch.

Posted by: rlorenz Nov 24 2019, 03:29 AM

<personal opinion only>
Despite being a proponent of Venus exploration (I am associated with one present Discovery proposal, as well as having involvement in international missions)
I find the case for a Venus flagship somewhat uncompelling : I wonder if it essentially was the result of the architecture of the Decadal Survey
(i.e. the (non-Mars) terrestrial planets could get one Flagship into consideration, and that's what popped out)

There is definitely a need for higher-resolution radar observations (Magellan's stated purpose was to map Venus as well as Mariner 9 mapped
Mars, so there's a little catching up to do...) with an emphasis on change detection (e.g. multiple revisits, interferometry etc.) and for in-situ measurements on and near the surface.

The synergy of combining these into a single mission (for which there are surely *some* advantages) is IMHO less strong than at more remote targets (I led the
science definition team for the first Titan Flagship study in 2007, which advocated a lander, a balloon and an orbiter - at the large Titan-Earth distance, the
orbiter really improved the data return from the in-situ elements) - the data relay enhancement of return from a lander is not so critical for non-mobile
landers which develop new information at a much lower rate than rovers/balloons etc., and for the smaller Earth-Venus distance.

The capability for near-surface in-situ missions (high P,T) used to be within the purview of the USA and USSR. It isn't clear that Russia today really has that capability, so
I'd expect the USA to be the lead behind any future lander.
(Balloons etc near the 1-bar cloud tops are less demanding : although the entry challenges are non-trivial, they are comparable with Earth entry, that
ESA, China, Japan etc. can handle)
Unless surface mobility, multiple (>2) landers, or sustained longevity is introduced, near-surface in-situ measurements are within Discovery/New Frontiers scope

Beyond their propulsive demands, orbiters require attentive thermal design, but are otherwise not terribly different from Earth orbiters. So the pool of countries /agencies
that could 'bite off' the radar/gravity/near-IR mapping job is not small. We have already seen promise that India may enter this arena (although I am skeptical that the
downlink bandwidth will allow an Indian mission - if anything like MOM - to do justice to radar mapping)

If an Indian mission happens (even just an orbiter with a range of payloads), and a 'proper' radar mission (ESA's Envision and/or a US Discovery class like VERITAS) and
an in-situ mission (e.g. Discovery or New Frontiers and/or Venera-D [but Im not holding my breath on that, V-D's been nothing more than vugraphs for about a decade now]
start development in the next few years, then Venus science in the next decade will be in decent shape. In which case I'd find it hard to argue for a Flagship, and I'd suggest that
such a 'coalition' of smaller missions is more likely to happen than a Flagship.

If India+Envision only, that'd be good, but there are some major questions still not being answered (surface/atmosphere chemistry for one, probably the noble gas abundances)
If only one of those, it amounts to 'life support' for Venus science at best. The Venera/VEGA/Pioneer Venus generation are basically all retired, the Magellan generation (i.e. those
professionally active while the mission was in operation) still has a reasonable fraction of people in the field that can offer direct experience to missions developed and launched
in the 2020s, but if it takes until 2030 to go back, much of the intellectual heritage of the earlier missions and questions will be lost.

There are doubtless aspects of the Venus climate whose understanding can be refined, but IMHO (see my book 'Exploring Planetary Climate') the basics were pretty well figured-out by Pioneer Venus and the Veneras. There is
new appreciation of time variability from VEx and Akatsuki, but again, good traction of much of that science can be made from smaller missions. I just don't see a Flagship.

Akatsuki is great (but its near-IR cameras ceased operation after a year in orbit, so it's just doing UV, thermal IR, lighting/airglow and radio occultations). The Bepi-Columbo
and Solar Probe flybys are cool and all, but don't provide a lot of data or answer any major questions.

</opinion>

Posted by: JRehling Nov 27 2019, 04:54 PM

Your opinions are gold, Ralph – very informative.

One thought on the engineering side that you didn't mention: Obtaining circular orbits via aerobraking or otherwise. Magellan began with a relatively low-eccentricity orbit attained with chemical propulsion, then used aerobraking to circularize the orbit for the gravity mapping phase. Since then, three U.S. orbiters and one ESA orbiter have used aerobraking to obtain a circular orbit at Mars.

Veritas and Envision would be the first mission(s) to use aerobraking to attain a circular orbit around Venus for a spacecraft's primary mission.

What I wonder is whether other space programs would have the capability to achieve this or if this seems like USA/ESA capability only for the time being. I realize that the question is potentially speculative, but seeing as the USA and ESA missions plan on it and the Indian mission does not it seems like a potentially significant distinction between proposed orbital surveys of the planet's surface.

For atmospheric science, this seems much less significant as time variation is important and a wide perspective is not a bad tradeoff.

Posted by: antipode Nov 28 2019, 10:34 PM

Ill second that, but...

...What would be the most cost effective way to get more information on the mysterious 'unknown UV absorber' in Venus' clouds?
Does this need in situ sampling, or can it be done remotely, and if the latter, is it in the reach of a larger cubesat?

(I'm assuming there wont be megabucks around for Venus missions in the near-mid term)

P

Posted by: scalbers Nov 29 2019, 12:51 AM

What's the story with disulfur oxide as a possible UV absorber as in https://pubs.rsc.org/en/content/articlelanding/2018/CC/c8cc00999f#!divAbstract? Then we have http://www.unmannedspaceflight.com/index.php?showtopic=8233&pid=232277&st=0&#entry232277.

Posted by: vjkane Nov 29 2019, 06:17 PM

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwjCoqm-g5DmAhWM4J4KHaLMAl4QFjAAegQIBhAC&url=https%3A%2F%2Fwww.lpi.usra.edu%2Fvexag%2Fmeetings%2Farchive%2Fvexag_15%2Fpresentations%2FCUVE%25E2%2580%2593CubeSat-UV-Experiment-Valeria-Cottini.pdf&usg=AOvVaw19Iv82YFTygDDN2qX_ixWn

Posted by: vjkane Nov 29 2019, 06:22 PM

The ESA/NASA EnVision mission, if selected, would as I remember, begin to deliver data from it's low orbit in something like 2033 to 2035 (don't have time to look up actual date). So another half generation plus of scientists would retire before data begins to flow.

A NASA mapper mission, if selected for the ~2024 Discovery launch date, would presumably deliver data beginning a year or two later (flight time to Venus plus aerobraking).

Posted by: JRehling Nov 29 2019, 10:11 PM

The OSSO abstract and CUVE proposal are both very interesting. I think what has allowed the identity of the UV absorber to remain indeterminate is the fact that the physical manifestation of the absorber is a wildcard: If it's not in a simple gaseous state, then the spectral properties of grains and droplets introduce complexity that is hard to account for. For example, if a solid particle has liquid droplets condense upon it, the resulting spectrum might be very hard to duplicate in the lab without knowing which permutation to look for. The lab work and something like CUVE are certainly positive steps forward, though. As the chromophores in the clouds of Jupiter and Saturn are also still unknown suggests how difficult something like this is to resolve.

It sticks in my mind that Venera 11 and Venera 12 found large amounts of chlorine in the clouds while Pioneer did not. That seems odd if chlorine were not part of what varies spatially and temporally in Venus' clouds. It seems to me like a clincher would be to have in situ cloud sampling measuring elemental composition occur at locations that are known to be, respectively, UV bright and UV dark would be the most definitive way to resolve the question. It would be nice to know, in retrospect, what the UV albedo was at the time and place of the Venera and Pioneer in situ measurements, but that information may be irretrievable.

Posted by: rlorenz Nov 29 2019, 11:13 PM

<opinion>
I don't doubt that UV spectroscopy so far is inadequate to identify the UV absorber, nor that it is an important element of the Venus climate. But I havent seen a persuasive case that a better UV spectrum would be able to unambigously identify it (your chromophore analogy is a good one), nor that a UV spectrometer is the best payload for a smallsat Venus orbiter. I could be wrong about both these things, but havent seen it yet.

I do believe that a UV spectrometer able to yield a better spectrum *could* be implemented on a smallsat, so in the context of SIMPLEX (i.e. 'what could you do at a planet with a smallsat that might be scientifically interesting? : the overall data volume needed is modest) a proposal like CUVE makes sense.

On the other hand, LUVOIR claims to be able to do good UV spectro-imaging at Venus too (see https://asd.gsfc.nasa.gov/luvoir/reports/LUVOIR_FinalReport_2019-08-26.pdf ). And/or maybe the Indian mission will have a decent UV spectrometer.

Even identifying the absorber from an in-situ mission will be challenging, but I'd venture that has a better chance (if it can sample the relevant altitudes) of providing a more definitive answer than any remote sensing would.
</opinion>

Posted by: JRehling Feb 22 2020, 04:16 PM

Until the other day, I had assumed that the DAVINCI proposal (now called DAVINCI+) in the current set of Discovery proposals was basically DAVINCI from last time around with a modest change. The reality is dramatically different. What they have added since last time is arguably larger than what was proposed before.

In a nutshell, the new mission proposal is more like a Messenger for Venus with an entry probe rather than just an entry probe. It would flyby Venus twice while holding the probe, make significant scientific observations in IR and UV, of both the atmosphere and the surface, before releasing the probe, then the carrier would enter Venus orbit and continue making observations long after the probe's mission was complete.

Many details here. I'm not sure how the IR emissivity science would relate to that collected by VERITAS, should both of them be selected. It seems almost certain that VERITAS would collect more and better IR emissivity science, but each of them is doing a lot more than that.

https://www.hou.usra.edu/meetings/lpsc2020/pdf/2599.pdf

Posted by: vjkane Feb 23 2020, 05:24 AM

Here’s a summary of the VERITAS VEM instrument

VEM [7] covers >80% of the surface in six NIR bands located within five atmospheric windows sensi-tive to Fe mineralogy, plus eight atmospheric bands for calibration and water vapor measurements, all with significantly enhanced SNR relative to the VIRTIS instrument on the European Space Agency (ESA) Venus Express mission.

And the DAVINCI+

A multi-band imaging system that includes UV, Near IR (1 um), and an engi-neering wide-field mode, has been incorporated onto the Lockheed-Martin carrier/telecom/orbiter space-craft, with opportunities to acquire first-ever vantage points on Venus in the UV (where the mystery absorb-er is lurking) as well as in night-side 1 m emissivity.

So the VEMS is a more capable spectrometer but lacks UV VERITAS also will be in a circular orbit and I suspect DAVINCI+ will be in an elliptical orbit

Posted by: JRehling Feb 23 2020, 06:00 PM

Good breakdown, Van.

The VEM approach is even more evolved and specific than a spectrometer in general. I won't pretend to have absorbed all of the details, but the design is based on analyses of Venus spectra and how the atmosphere absorbs different IR wavelengths so that new imagery in five specific IR windows can be processed to cancel out the noise from the atmosphere and provide a meaningful six-band spectrum of the entire surface at what would effectively be ~50km/pixel. That's much worse than our radar imagery, but if you picture a 12 inch/30 cm globe of Venus, those pixels are just 2 mm, which is quite nice. The six bands should be sufficient to distinguish different surface compositions (both the origin of the rock and its chemical weathering are relevant). The resulting map of Venus' surface, for the first time, in "color", will be practically a new planet compared to any data we have previously received. (VIRTIS data allowed a bit of this analysis, but with fewer spectral bands; it, however, provided the data that allowed for the design of the VEM approach.)

I think a decent analogy is that it will do for Venus was MGS' TES instrument did for Mars. It won't have the spatial resolution that VIMS had at Titan, but comparable spectral resolution. It would likely identify for us any recent lava flows on Venus and possibly their ages, as well as a compositional map of the whole surface. It is simply unlike any data we currently have and probably could not be improved upon without airships operating below the clouds.

Posted by: mcaplinger Feb 23 2020, 07:06 PM

Could do, maybe, if it gets selected and if the massive complication of removing atmospheric signature actually works.

But perhaps I'm biased.

Posted by: vjkane Feb 24 2020, 02:16 AM

In the previous discovery competition, proposers in phase a could suggest enhancements that NASA could decide to fund it not. For example, jpl was going to propose the Cupid atmospheric robe for the previous VERITAS proposal. (I have no idea if this is true for this round). I wonder if DAVINCI+ might propose VEMS (it would be DLR supplied), and VERITAS the CUVE UV spectrometer ( it’s only 1-2 U in size)

Posted by: JRehling Feb 25 2020, 07:12 PM

Skepticism noted, Mike! Certainly the VEM instrument's success is subject to the yet-unknown realities of Venus itself, not only the atmosphere, but also the surface. It is exploration.

Is there any detail public yet about the nature of the DAVINCI imaging? I suppose one simple question I can't shake is whether it would all be down-looking or if there would be any side-looking panoramas made after or near touchdown.

Van, interesting thoughts about add-ons. It seems like DAVINCI has added a lot from the last time. I also would note that VERITAS, in utilizing a near-circular orbit, might therefore be pushing mass margins, but it would use aerobraking to achieve that orbit. Adding mass would make that more challenging, but the devil is in the details.

Posted by: mcaplinger Feb 25 2020, 10:41 PM

There are a variety of public papers and LPSC abstracts about the 2016 incarnation of DAVINCI from which inferences can be made. I'm not free to say anything about what might have changed, sorry.

Posted by: JRehling Feb 26 2020, 03:25 AM

I thought that was the likely response, but you can't blame a Venus fanatic for trying!

Posted by: vjkane Feb 27 2020, 11:33 PM

I can't find the link, but the previous DAVINCI imager would have built up overlapping images that would have allowed photogrammetric point matching to create 3D surfaces from the images. The presentation I remember showed that at high resolution. I don't know if it could have been done from higher elevations over wider areas.

From the one DAVINCI+ abstract available, it looks like they are supplementing the visible imager with a near infrared imager to relate finer scale composition to what would be seen from orbit.

Posted by: dtolman Sep 13 2020, 01:00 PM

If NASA (Congress) decides they are VERY interested in a out-of-cycle flagship or new frontiers class mission to Venus by middle of this decade to look at the... chemistry... of its atmosphere - do they collect new proposals, revisit the New Frontiers class missions that were turned down in 2019, or look at upscaling the current 2 Discovery class contenders?

I imagine that any proposed mission that wants to take a close look at the atmosphere's... composition... will want to include a sample return capsule or a balloon with an extensive chemistry lab on board. ISRO may be rethinking their decision not to include the atmospheric balloon on its payload as well.

Posted by: vjkane Sep 13 2020, 01:16 PM

NASA and Congress follow the priorities set in the Decadal Surveys. Unless the new survey prioritizes a Flagship Venus mission, it almost certainly won't happen. The one exception to this rule I can think of was former Congressman Culberson's insertion of the Europa Clipper mission into law (and the budget) along with a follow on Europa lander. The Clipper mission was the Decadal Survey's #2 flagship priority, so he was supporting the Decadal Survey's priorities there. The lander was not a Decadal priority, and while excellent mission definition work continues, Congress isn't providing the funding to take it to development anytime soon.

However, Culberson was an exception, probably unique in both his strong interest and his powerful position that allowed him to push Clipper through. Usually when someone in Congress backs a NASA mission ardently, it is because it brings a lot of $s and jobs to their state or district (such as Senator Shelby's strong support for the SLS).

All that said, the next Decadal Survey may continue to prioritize a Venus mission in the New Frontiers line, and good missions can fit into the Discovery line (a number of Venus atmospheric missions have been proposed for the Discovery program). And don't count out the SIMPLEx program. There are some exciting cubesat-scale atmospheric instruments in development to study Venus' atmosphere.

Posted by: JRehling Sep 13 2020, 09:41 PM

If either or both current proposals for Discovery missions to Venus succeed, then that would certainly change the balance sheet of outstanding scientific questions regarding Venus. They would also almost certainly raise new questions regarding Venus' surface and reorder the list of Venus priorities in ways that are difficult to foresee. Record of ancient sea floors? Active volcanoes? Something pertaining to the commonality of the origins of Earth's and Venus' respective atmospheres? I think it's likely that any Discovery mission would give us new information that would take time to gestate and would push any possible Venus flagship mission further into the future.

Posted by: Explorer1 Sep 14 2020, 01:44 AM

Given that Venus is already trending on Twitter (and it is not entirely about tennis), I expect public interest would definitely play a role in whether a major mission will be funded, "changing the balance sheet" as you put it.
I do wonder how a sample return from the atmosphere could be affected. Possibly even trickier then Mars sample return. An airship or balloon with a solid stage to carry a capsule to orbit for rendezvous and Earth return?

Posted by: JRehling Sep 14 2020, 01:57 AM

Multiple options for Venus atmospheric sample return are discussed here.

The DAVINCI+ Discovery proposal would measure Venus' atmospheric composition in situ with unprecedented accuracy. Until we know what that might find, we can't say if it would address many of the questions regarding Venus' atmospheric composition or if it would raise new ones.

Also note that an in situ measurement from the lower atmosphere could answer some questions better than a sample return from the upper atmosphere at certainly less cost.

https://www.hou.usra.edu/meetings/V2050/pdf/8164.pdf

Posted by: dtolman Sep 14 2020, 03:28 PM

Well - its officially released now. Phosphine gas has been found at the mid-latitudes (but not the poles) of the Venusian atmosphere by two different telescopes (very definitively by the ALMA array). There are no *known* abiotic processes to produce the concentrations found (up to 20 parts per billion).

So I imagine that the immediate focus from a space robotics perspective will be on the private Rocketlab and Indian missions which are both slated for launch in 2023, to see if they could get a more specific data on phosphine concentration at different altitudes and latitudes, and its chemical precursors.

Posted by: mcaplinger Sep 14 2020, 03:35 PM

Phosphine has been detected in the atmospheres of Jupiter and Saturn without exciting much comment I'm aware of. https://ui.adsabs.harvard.edu/abs/2009Icar..202..543F/abstract

Posted by: dtolman Sep 14 2020, 03:43 PM

The paper is paywalled, but https://arxiv.org/ftp/arxiv/papers/1910/1910.05224.pdf2019 paper on phosphine discusses that the pressures found at Jupiter and Saturn can produce this abiotically - but these conditions are not found on terrestrial sized planets (not even Venus) according to the discussion within the paper:

Theformation of PH3 on temperate, rocky planets is thermodynamically disfavored, even in high-reducing environments, unlike the fermentative
production of methane or hydrogen sulfide. In thermodynamic equilibrium,phosphorus can be conservatively expected to be found in the form of PH3
only at T > 800K, and at P > 0.1 bar (Visscher et al. 2006), which is why PH3 has been detected in Jupiter and Saturn, where these extreme temperatures
occur (in the deep layers of the atmosphere). We also note that the critical temperature of water is 647 K so there are no surface conditions that favor
both PH3 production and allow for the presence of liquid water

This chemistry was discussed in their press briefing just now as well.

Posted by: Explorer1 Sep 14 2020, 03:45 PM

RAS briefing here is still going:
https://www.youtube.com/watch?v=y1u-jlf_Olo

Posted by: centsworth_II Sep 14 2020, 04:41 PM

https://www.nature.com/articles/s41550-020-1174-4

Posted by: dtolman Sep 14 2020, 04:45 PM

So putting aside the out-of-forum scope questions... are their instruments planned on the upcoming Indian mission to Venus - or the two Discovery candidates (DAVINCI+, VERITAS) that are capable of detecting phosphine gas in the atmosphere? If not, are any suitable with modification? Or will this require instruments designed from the ground-up - or even a dedicated in-atmosphere mission - to better answer this question?

The team mentioned during the press conference they were working with RocketLab's 2023 Venus team - so presumably it will carry *something* that can help confirm the result, and further refine where phosphine is in the atmosphere.

Posted by: mcaplinger Sep 14 2020, 04:46 PM

It will be an interesting moderator challenge to figure out how, or even if, this discussion can occur in light of rule 1.3.

Posted by: JRehling Sep 14 2020, 04:51 PM

The phosphine news release led me to write some, I assure you, very funny and snarky comments that I won't post because of board rules, but in the realm of the safe-to-say: Venus has conditions well different from Earth's and undoubtedly, some interesting chemistry different than the chemistry here.

We still await a mission that performs Venus in situ surface science as thorough as Viking provided at Mars and the old conundrum one can't ignore is that temperatures require a viable strategy for survivability; there is a set of distinct strategies for making that work; as far as I know, there's no doubt that more than one of the strategies is viable, but nothing is going to come to fruition until a mission picks one of them and gets funded.

IMO, making a virtue of necessity, a mission architecture that seems promising for surface analysis is an aerobot that makes very short stays on the surface to grab samples, then inflates a helium balloon, ascends to cooler and survivable temperatures, performs analysis, and transmits results back to Earth while floating near cloud level. Winds at the cloud level could transport the craft almost unlimited distances downwind for touching down on and analyzing a second, etc. location. This would be in many ways analogous to Dragonfly at Titan, but with much greater capability for horizontal transport. One mission could conceivably visit all of the major terrain types on Venus – plains, tesserae, recently active volcanic surface, radar-reflective high altitude regions. With any other architecture, we would hope to drop two or more stationary landers and begin to understand the surface chemistry.

For a "Venus Insight" mission that includes a seismometer, I think it's a lot more hopeful that robust electronics could operate a surface station for long durations.

We are about a year away from learning if Venus scores one or two Discovery missions that would be preliminary to whatever next-generation surface mission.

Posted by: JRehling Sep 14 2020, 05:13 PM

It seems to me that phosphine at Venus is analogous to methane and other phenomena at Mars: We can make spectacular leaps in hypothesizing, but we're at an early point in the understanding and there's no doubt that we'd all like to understand the origin of methane at Mars and phosphine at Venus. How spectacular or mundane reality turns out to be is a matter that we don't control.

Posted by: mcaplinger Sep 14 2020, 05:21 PM

I'm not believing that this technology will be practical any time soon. See https://www.hou.usra.edu/meetings/exoplanets2020/presentations/Gilmore.pdf for the current thinking of what could be done with a flagship budget, which has a goal of a lander that lasts 4-8 hours and a 30-day minimum lifetime balloon.

Posted by: Bjorn Jonsson Sep 14 2020, 05:43 PM

I noticed that someone asked about this at the RAS briefing. The reason if I understood correctly is different conditions at Jupiter and Saturn: Lots of hydrogen and much higher pressure where the phosphine forms.

Posted by: stevesliva Sep 14 2020, 06:44 PM

As JRehling said, history shows we can civilly talk about the elephant in the room (methane spikes), you just can't argue about whether the elephant is biogenic. That's fine by me.

Posted by: Gerald Sep 14 2020, 08:58 PM

A fully anorganic approach I could offer is a release of PH3 by the reaction of a phosphide mineral with sulfuric acid similar to https://en.wikipedia.org/wiki/Iron_phosphide:
"Iron phosphide reacts with moisture and acids producing phosphine (PH3), a toxic and pyrophoric gas."

I'd consider https://en.wikipedia.org/wiki/Schreibersite one of the more plausible candidates.

mindat.org says: https://www.mindat.org/min-3582.html ((Fe,Ni)3P): "The mineral is estimated to stand for 1-10% of the total crustal phosphorus during the Hadean."
So, it might exist in Venus' subsurface, as well. Or it is added by https://www.nature.com/articles/srep08355 impacts.
"Phosphide minerals are common accessory phases in meteorites and, to a lesser extent, in lunar rocks, interplanetary dust particles and comets."

All we need is a mechanism to get the presumed phosphide mineral in contact with the droplets of sulfuric acid in Venus' clouds.
Three mechanisms might be conceivable:
- meteorite impacts,
- dust / regolith stroms, or
- volcanic activity.

I might have overlooked a discussion of these phosphide mineral - acid reaction paths in the paper or in https://static-content.springer.com/esm/art%3A10.1038%2Fs41550-020-1174-4/MediaObjects/41550_2020_1174_MOESM1_ESM.pdf (p.11 ff.). I think, that the authors implicitely discarded this option due to the oxidizing environment of the atmosphere. But I'm not sure whether one can make such a simple assumption, especially for freshly exposed material.
Fresh exposure of (reduced) phosphide minerals would at least sound more plausible than a highly complex organic chemistry, which would require to sustain reduced compounds in an oxidizing environment, too.

Posted by: ollopa Sep 14 2020, 09:06 PM

Might there not be data in the VEX SPICAV archive that could help?

Posted by: mcaplinger Sep 14 2020, 09:16 PM

These observations were made at wavelengths of around 1mm, much longer than any remote-sensing instrument that's been flown to Venus AFAIK (SPICAV only goes to 4.3 um). You need to penetrate down to the 50-km level, and you probably can't do that at shorter wavelengths. Which puts in situ measurement at a distinct advantage.

Posted by: Ron Hobbs Sep 15 2020, 03:38 AM

Will the BepiColombo flyby coming up in a month be able to confirm this observation? Here is a quote from an ESA release:

Yeon Joo Lee, said: “The opportunity to use all these instruments simultaneously will give us access to multiple wavelengths to probe different altitudes of the atmosphere and to distinguish the different gases present. Simultaneous observations from a close-up to a global view mean that we can study physical processes on the planet at a variety of scales, from convection across a few tens of kilometres to global circulation patterns. The different viewing angles and distances of all the spacecraft and telescopes involved will enable us to see what’s happening on the dayside and the nightside of the planet and how processes evolve over time, which can be missed by just one mission.”

They talked about Earth-based observations to support the flyby, but I don't know if they will happen now with Covid-19.

Posted by: rlorenz Sep 15 2020, 04:17 AM

There was a very analogous media tizzy a little over a decade ago about altitude variation of hydrogen on Titan. There are two challenges in this sort of situation, detection and attribution.

First, detection - is this really phosphine on Venus (and not some non-Doppler-shifted deuterated terrestrial phosphine line - Zahnle attributed one of the Mars methane detactions to this effect) or some other measurement artifact. The history of planetary science is replete with spectroscopic detections that turned out to be spurious. Radio/millimeter seems to be a bit better in this respect than the near-IR

Then (qv Sagan 'extraordinary claims require extraordinary evidence') is the signature exclusively attributable to a biotic process? This is a high bar. e,g, one can attribute methane on Mars to (abiotic) serpentinization reactions of water with hot rock. How much is at a level that requires a biogenic source? When one starts to look at these things quantitatively, the life/non-life boundary becomes very fuzzy. The paper makes an attempt to consider some alternative formation mechanisms, but it is difficult to know that you have addressed 'unknown unknowns' adequately.

Funding agencies and institutions like the press. The journals like the attention. The media reporting on the journal article like the buzz and the advertising $$. All the incentives are to talk up observations like this (and to ignore whatever caveats the authors expressed in their original discussion). So, while I dont deny Venus can use some more attention, some skepticism on the interpretations in this report is in order.

Posted by: mcaplinger Sep 15 2020, 05:53 PM

Seems pretty unlikely. The longest wavelength it can observe is the thermal infrared to about 14 um. I haven't been able to find what the spectrum of phosphine looks like at visible to thermal IR wavelengths, but this would require there to be windows at the appropriate wavelengths for general atmospheric scattering and absorption, and enough SNR to be able to detect absorption lines.

Posted by: dtolman Sep 15 2020, 06:57 PM

Not yet mentioned on this site - but private rocket/satellite company Rocketlab has committed to running a privately funded mission to Venus on its Electron rocket using its Photon satellite platform during the 2023 launch window. Budget is in the 10's of millions, and https://www.bbc.com/news/science-environment-54151861. In other interviewshttps://www.nytimes.com/2020/09/15/science/venus-life-rocketlab.html

Posted by: mcaplinger Sep 15 2020, 07:13 PM

It's very unclear to me what "committed" means, and I see a lot of naive talk about how easy it would be to pull something like this off. But if you like that sort of discussion, I suggest https://forum.nasaspaceflight.com/ as a better venue.

Posted by: Gerald Sep 15 2020, 09:30 PM

The most intense vibrational absorption bands seem to be centered to wave numbers 2321.1314 cm^-1 and 2326.8766 cm^-1, see table 1, page 7020 in https://www.researchgate.net/publication/234998185_The_stretching_vibrational_overtone_spectra_of_PH3_Local_mode_vibrational_analysis_dipole_moment_surfaces_from_density_functional_theory_and_band_intensities.
If I calculated correctly, this should correspond to a wavelength of about 4.3 um.
I didn't find longer vibrational wavelengths, and I didn't make an attempt to understand https://arxiv.org/pdf/1305.1138.pdf.

Posted by: mcaplinger Sep 15 2020, 10:07 PM

There's a huge CO2 absorption right there, so that doesn't seem viable. See Figure 5 in https://arxiv.org/abs/2003.00228

But I'm no expert. I'm sure all of the orbital datasets will be getting a close look in the months ahead and people will be considering what types of remote sensing would be best suited (if any.)

Posted by: JRehling Sep 15 2020, 11:20 PM

re: Phosphine on Venus as biogenic:

If someone familiar only with Europe looked at the Moon through a telescope, they might conclude that it was covered with volcanoes, because big, circular holes in the ground in Europe always mean volcanoes.

In fact, that's exactly what European astronomers did conclude of the Moon. And it was wrong. It's just not a valid form of reasoning to conclude that.

Now, there are volcanic craters on the Moon, and there are impact craters on Earth. If you see one crater on the Moon, "volcano" is a fine hypothesis to put on the list. But that's where it stops before you acquire more evidence.

Posted by: mcaplinger Sep 15 2020, 11:29 PM

I'm not following the point you're trying to make at all. The paper attempts to show why non-biogenic origins are not possible under Venusian conditions. You can take issue with how complete this attempt was, but they certainly made it.

Posted by: marsbug Sep 16 2020, 01:00 AM

That's a valid point but I'm not sure why you make it here? In fairness to the authors of the paper they haven't concluded there is life the Venusian clouds, they only advance it as one hypothesis of several that might fit this data. They attempt to rule out some others, and happily admit there's a huge slew of known unknowns and unknown unknowns surrounding the detection and origin of this phosphine, when asked.

Even if we could rule out a biogenic origin right this instant, the presence of phosphine adds another mystery to the Venusian chemical environment - which is already known to be a complex, ever changing, environment with lots of mysteries already, and direct relevance to our efforts to better understand Earth and it's history. So I'll admit to being excited at the thought it might start to receive more attention.

Posted by: nprev Sep 16 2020, 02:47 AM

ADMIN NOTE: Everybody play nice...which is another reason for the existence of rule 1.3.

Posted by: stevesliva Sep 16 2020, 02:49 AM

The analogies and arguments about how much skepticism is warranted should be avoided. The https://xkcd.com/2359/ tries to cover the bases there. (Think of the xkcd as 9 squares of strawmen being built up to get torn down, so... don't do it.)

I struggle to understand what this observation was, exactly, so I think the discussion of what other assets might replicate it the most interesting and on topic here.

What might be most informative is... why hasn't anything else seen it before? Or has it been seen before, just not noted?

Posted by: stevesliva Sep 16 2020, 03:09 AM

Aha. This layman had been wondering about SOFIA, and thishttps://www.reddit.com/r/space/comments/ismj49/phosphine_gas_in_the_cloud_decks_of_venus/ (where you are free to go argue about whether other people are more or less excited than they should be), his this tidbit:

Nicely pullquoted from a NG article that I didn't read because I didn't want their spam:
https://www.nationalgeographic.com/science/2020/09/possible-sign-of-life-found-on-venus-phosphine-gas/

Posted by: Bjorn Jonsson Sep 17 2020, 12:15 AM

The UMSF moderating team has been discussing the recent Venus news in the context of rule 1.3 (which I assume everyone here is familiar with ;-).

The result is that it has been decided to relax rule 1.3 a bit in this thread, at least temporarily. This means that discussion of instrumentation and methods is entirely appropriate, and of course the purpose of some of the instruments would be to detect biosignatures (this means that it is perfectly OK to mention biosignatures in the discussion).

We need to emphasize the following, though:

1. Anybody claiming the discovery of life will be booted (no "unsung basement genius" bullshit).

2. Organic chemistry in the context of signatures is okay, but not extrapolation based on findings since that can get stupid quickly. This includes linking to the inevitable torrent of imaginative 'life in the clouds of Venus' nonsense articles that will shortly pop up all over.

3. Discussions that veer into sheer speculation (or even crackpot theories) will be shut down immediately.

Now let's have fun discussing possible future Venus missions etc. which suddenly have become a whole lot more exciting! (and even before this I found many of them interesting, e.g. DAVINCI+, VERITAS and EnVision).

Posted by: Phil Stooke Sep 17 2020, 07:49 AM

How about this?

Phil

Posted by: dtolman Sep 17 2020, 12:09 PM

Wondering about whether VEX could have picked up signatures, https://www.forbes.com/sites/brucedorminey/2020/09/15/venus-life-is-still-a-longshot/#40d685381cd5 - could VEX's VIRTIS have collected evidence of Phosphine's presence already?

Phosphine has an absorption band in the infrared spectrum at roughly 3.05 microns, Julie Castillo, a planetary scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, told me. So, one should check the observations of the VIRTIS instrument on Venus Express for the possible presence of that phosphine in its VIRTIS observations, she says.

Posted by: JRehling Sep 17 2020, 03:55 PM

It has been well noted that the SO2 composition of Venus' atmosphere has varied dramatically over the duration of observations. It remains possible that the phosphine detected on Venus in 2017 wasn't present when Venus Express ended in 2014. (I'm not sure when VIRTIS last took measurements, so the EOM in 2014 may not be the relevant start of the window between last Venus Express measurement and the phosphine detection.

The Sousa-Silver paper notes that "phosphite can disproportionate to phosphine at T > 323K and acidic pH." If a volcanic event on Venus liberated phosphorus-bearing minerals in the last few years, the detection of phosphine could record a very temporary event.

In fact, I wonder if Venus provides a loophole here that hasn't been discussed (Sousa-Silver, et al were talking about exoplanets in general, not Venus), that a non-volcanic mass movement event on Venus (earthquakes, landslides) could introduce subsurface minerals to surface conditions and begin chemical reactions at the time of the event. The "acidic pH" condition might be met at the surface, but not in the subsurface. No volcano required. No inherent paradox that a gas that should be destroyed quickly in Venus' atmosphere is present now.

From my armchair (I am literally sitting in an armchair right now), VERITAS would likely provide better insight as to the rate and recency of mass movement events on Venus, while DAVINCI+ obviously provides different opportunities to investigate the phosphine result.

Posted by: Gerald Sep 17 2020, 04:39 PM

https://en.wikipedia.org/wiki/Phosphorous_acid#Disproportionation is thermally decomposed ("disproportionated") into PH₃ and H₃PO₄ near 200°C.
If there would exist some catalytic process in the presence of H₂SO₄ and CO₂ to recover the H₃PO₃ from H₃PO₄, we would get a closed cycle, depending a bit on the oxidation products of PH₃, and less supply from exogenic sources would be required.
Just to get rid of that one easy-looking O is probably the point where some "new chemistry" is needed. At least I wasn't able to find a paper describing or providing at least a hint how to track this way back.

Posted by: mcaplinger Sep 17 2020, 05:27 PM

To detect something in absorption, you have to 1) know where the absorption is, and then 2) you have to have a light source that would normally have a lot of energy at that wavelength (either reflected sunlight or thermal emission, depending on wavelength) and 3) it can't be absorbed or scattered by the other stuff between the instrument and the target, and 4) the instrument has to have enough SNR and spectral/spatial resolution to detect the absorption.

1 depends on the behavior of the substance under venusian conditions (if that's known; phosphine is horrifically toxic so people may not have enthusiastically studied it in the lab, I sure wouldn't); 2 and 3 depend on the complex properties of the atmosphere above (and for emission, below) the clouds; 4 is usually something the instrument designers know.

As I said upthread, I'm sure this will be gone over carefully for every dataset there is, and we'll see what happens.

Posted by: Explorer1 Sep 18 2020, 01:24 AM

We might not need to wait that long for new atmospheric data: Bepicolombo has two flybys coming up (this October and next August), and the MERTIS instrument does have the spectral range to attempt observations. The main hurdle is resolution; the August flyby is more likely to make any phosphine detection as it is only going to be 500 km away vs 10,000 for the first flyby https://www.forbes.com/sites/jonathanocallaghan/2020/09/16/in-a-complete-fluke-a-european-spacecraft-is-about-to-fly-past-venus--and-could-look-for-signs-of-life/#3b1c9bb32681

Posted by: JRehling Sep 19 2020, 05:19 PM

It occurred to me yesterday that the phosphine is the second mystery of Venus that (may) relate to potassium, or at least to elemental composition in the same part of the periodic table.

Venus has an extremely high ratio of 36Ar/40Ar compared to that on Earth, reflecting a somewhat lower amount of 40Ar but a much higher amount of 36Ar. 40Ar is produced by the radioactive decay of 40K, so this seems to indicate that the Venusian atmosphere has had less interchange with any reservoir containing 40K.

That said, this doesn't point in the same direction as any excess of potassium, and even if it did, 40K is a very small fraction of terrestrial potassium anyway. This is also a comment on nuclear chemistry, not the chemistry that produces/sustains phosphine. What it does say is that the elemental composition of the Venusian atmosphere and crust is not like Earth's in some striking ways. If 36Ar can be superabundant on Venus, could 39K (related in no causal way that I see) also be superabundant? And if so, that could help boost the signal that we're seeing here.

Venera 8 and Venera 13 both reported high levels of K in the surface, while the other five sites tested reported low K. It seems to me like we need more and better understanding of venusian crustal composition and landing on one or two new sites isn't going to resolve the issue. Perhaps emissivity maps from Veritas could use the Soviet data to ground truth maps of surface composition. Failing that, we would need more surface probes or, as I suggested before, one with great mobility.

Posted by: Gerald Sep 19 2020, 10:37 PM

Isn't this a straightforward consequence of the much higher mass of the atmosphere (including Ar-36) of Venus compared to that of Earth, with composition (especially Ar-36 ratio of the atmosphere and bulk K-40 ratio in the planet), and planet mass and density otherwise assumed to be initially almost the same? Both planets would then produce the same amount of Ar-40 and release it to atmospheres of very different mass, especially of Ar-36.

Posted by: JRehling Sep 20 2020, 03:35 PM

There's no consensus on why Venus shows the isotopic balances that it does, and some explanations suppose that Venus has simply never outgassed all of the Ar-40 it has inside. With rarer noble gases, we don't even know the isotope ratios, and determining those is a major motivation for the DAVINCI+ probe, which will let us check the validity of hypotheses regarding argon.

Posted by: Phil Stooke Sep 30 2020, 12:17 AM

https://arxiv.org/abs/2009.12758


Maybe Phosphine in Pioneer Venus Probe data! (still of unknown origin)

Phil

Posted by: Gerald Sep 30 2020, 07:40 PM

... obtained with the entirely different method of mass spectroscopy.
Plus hints towards traces of reduced species like molecular hydrogen, hydrocarbons, e.g. methane, the not fully oxidized species NO, and molecular oxygen O₂.
And if it's "only" unknown chemistry, we could learn something from accurate und unabiguous in-situ measurements.

Posted by: vjkane Oct 16 2020, 08:55 AM

Another team observing Venus in the thermal infrared has failed to detect phosphine, suggesting an upper limit on concentrations several times lower than that suggested by observations at millimeter wavelengths.

http://astrobiology.com/2020/10/a-stringent-upper-limit-of-the-ph3-phosphine-abundance-at-the-cloud-top-of-venus.html

Following the announcement of the detection of phosphine (PH3) in the cloud deck of Venus at millimeter wavelengths, we have searched for other possible signatures of this molecule in the infrared range.

Since 2012, we have been observing Venus in the thermal infrared at various wavelengths to monitor the behavior of SO2 and H2O at the cloud top. We have identified a spectral interval recorded in March 2015 around 950 cm−1 where a PH3 transition is present.

From the absence of any feature at this frequency, we derive, on the disk-integrated spectrum, a 3-σ upper limit of 5 ppbv for the PH3 mixing ratio, assumed to be constant throughout the atmosphere. This limit is 4 times lower than the disk-integrated mixing ratio derived at millimeter wavelengths.

Our result brings a strong constraint on the maximum PH3 abundance at the cloud top and in the lower mesosphere of Venus.

T. Encrenaz (1), T. K. Greathouse (2), E. Marcq (3), T. Widemann (1), B. Bézard (1), T. Fouchet (1), R. Giles (2), H. Sagawa (4), J. Greaves (5), C. Sousa-Silva (6) ((1) LESIA, Observatoire de Paris, PSL Université, CNRS, Sorbonne Université, Université de Paris, (2) SwRI, (3) LATMOS/IPSL, UVSQ Université Paris-Saclay, Sorbonne Université, CNRS, (4) Kyoto Sanyo University, (5) School of Physics and Astronomy, Cardiff University, (6) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology)

Comments: Astronomy & Astrophysics, in press
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2010.07817 [astro-ph.EP] (or arXiv:2010.07817v1 [astro-ph.EP] for this version)
Submission history
From: Bruno Bézard
[v1] Thu, 15 Oct 2020 15:11:37 UTC (805 KB)
https://arxiv.org/abs/2010.07817
Astrobiology, Astrochemistry,
Modify message

Posted by: Xerxes Oct 16 2020, 05:34 PM

The https://arxiv.org/abs/2009.06593 attempted to pre-rebut this argument:

This paper makes some arguments as to why the original signal would actually have to be at high altitude:


I suppose one would need a great deal more expertise to know whose argument is stronger.

Posted by: JRehling Oct 16 2020, 08:01 PM

One also needs to know if "high" and "relatively high" are referring to the same altitudes or if there's some important difference there. I would guess that anything above the clouds, encountering direct solar UV, qualifies equally well as "high" for these purposes, but I never received a paycheck for studying Venus.

Posted by: rlorenz Oct 17 2020, 03:10 AM

Expertise, maybe. But as humans, we can also employ our heuristic tools of caricature, profiling and prejudice.

Therese Encrenaz has been in *planetary* spectroscopy a long time. I think (and my Planetary Climate book gives many examples) in planetary science there are many instances of spectroscopic detections being disproved by in-situ or other data, which make some people (like her) cautious. In stellar astronomy (which seems to be where the Cardiff group has more pedigree), I could imagine there are fewer disproved 'discoveries' just because there are fewer ways to confirm or refute initial announcements.

So, IMHO, if Therese says it isnt in her data, then it isnt in her data... (and knowing her, she wouldnt say it wasnt there on Venus, only that there wasnt evidence for it in her data).

It may be non-PC to consider such meta-factors, but at the hairy edge of detectability, one is obliged - Bayeswise - to weigh all the information.

There are sadly a lot of incentives in the journals and the media to talking up anything that could bear on life in the universe - indeed Nature Astronomy even had an editorial congratulating itself on how much press the paper had generated and how this was only possible because of their media embargo policy. Cui bono....

All this said, Venus deserved the attention.

Posted by: Greenish Oct 27 2020, 11:35 PM

For what it's worth, this is new on the arxiv, not yet refereed:
Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine
I.A.G. Snellen, L. Guzman-Ramirez, M.R. Hogerheijde, A.P.S. Hygate, F.F.S. van der Tak
https://arxiv.org/abs/2010.09761

"...The reported 15σ detection of PH3 1−0 is caused by a high-order polynomial fit that suppress the noise features in the surrounding spectrum. ...Low-order spectral baseline fitting shows a feature near the expected wavelength at a signal to-noise of only ∼ 2."

It does come with a front page caveat that there has since been an update to the ALMA processing pipeline [while this re-analysis was in work], that they haven't fully analyzed. It notes that though many of the "spurious ripples" are gone, they still see no clear PH3 feature.

Posted by: antipode Nov 23 2020, 03:24 AM

Here's a Venus mission concept I hadn't seen before (apologies if its been covered further back).

https://www.hou.usra.edu/meetings/vexag2020/pdf/8045.pdf

Its a fascinating idea with potential high return, but I worry about that long cable and any shear/turbulence in between the baloon and the descent module.

P

Posted by: vjkane Nov 23 2020, 02:29 PM

Fixed URL link

This abstract discusses a similar idea:

http://url="https://www.hou.usra.edu/meetings/vexag2020/pdf/8031.pdf Investigating the Surface of Venus from Beneath the Clouds [#8031]
VeCaTEx would use an aerobot to descend repeatedly beneath the dense clouds for imaging targeted area of the surface in the near infrared spectral region to address six of the prime investigations prioritized by VEXAG.[color="#FF0000"][/color]

Posted by: vjkane Nov 23 2020, 09:27 PM

Moderators: I obviously had problems editing my previous reply and don't see a post delete button (sure I'm just missing the obvious). Please delete duplicates.

This is the correct link for the other poster at the recent VEXAG meeting for a mission concept that would go beneath the clouds for a more detailed examination of the surface.

https://www.hou.usra.edu/meetings/vexag2020/pdf/8031.pdf: Investigating the Surface of Venus from Beneath the Clouds [#8031]
VeCaTEx would use an aerobot to descend repeatedly beneath the dense clouds for imaging targeted area of the surface in the near infrared spectral region to address six of the prime investigations prioritized by VEXAG.

Posted by: JRehling Nov 23 2020, 10:07 PM

As a non-mechanical engineer, I nonetheless share antipode's sense that a cable more than 20 km long seems to introduce some serious worries about practicality. I can't even picture something like that working on Earth, much less being transported to Venus.

Here's an informative analysis of aerobot architectures. I'd never heard of nor thought of some of these architectures.

https://dartslab.jpl.nasa.gov/References/pdf/2019-BalloonTitanVeinus.pdf

We are, apparently, about three months away from finding out whether Venus will prevail in the upcoming Discovery mission selection, and the ESA decision on Envision was said, in 2018, to be expected "in 2021." So the next few months will have profound impact on the course of Venus exploration, with anywhere from zero to three missions in the balance depending on those decisions.

Posted by: mcaplinger Nov 23 2020, 10:45 PM

To put it mildly. At any rate, most of the concepts are just for a balloon that can change altitude by various means (see https://www.lpi.usra.edu/vexag/reports/Venus-Flagship-Mission_FINAL.pdf sections 3.2.3 and B.2.8.1 for one such concept).

Posted by: Gerald Nov 24 2020, 02:21 AM

I was wondering whether any fiber is known to be strong and heat-resistant enough, and found https://en.wikipedia.org/wiki/Aramid, e.g. https://en.wikipedia.org/wiki/M5_fiber, possible candidates. I'm just not sure whether thin fibers would also be sufficiently weathering resistant under the harsh environmental conditions in the Venus atmosphere.
This is before thinking about the dynamics of such a tether in a dense and stormy atmosphere.
In space in Earth orbit, at least, https://www.nasa.gov/centers/marshall/pdf/337451main_Tethers_In_Space_Handbook_Section_1_2.pdf.
(https://en.wikipedia.org/wiki/Space_tether_missions)

Posted by: mcaplinger Nov 24 2020, 04:15 AM

I've talked with people who worked on TSS-1 and -1R and they had quite a few stories about it. Let's just say that I don't think tether technology is quite ready for a Venus mission.

Posted by: JRehling Nov 27 2020, 12:26 AM

Reading the afore-linked reports, I think I've been disabused of the notion that an idealized aerobot, allowing for mobility at the surface, would be implemented anytime soon. It's possible in principle, but isn't part of the VEXAG report, and the complexity of more modest aerobot concepts implies the greater complexity of surface-to-clouds-and-back aerobots.

One important pragmatic consideration: Descent is more expensive than ascent, requiring energy to compress the helium and generally being rate-limited, while ascent is comparatively cheap and easy. For hypothetical missions that would cool at height and then descend and operate quickly, this would be a problem because there would be substantial thermal load accumulating during the slow descent.

The most modest aerobot/balloon missions would be, like the Soviet Vega balloons, operating only at high altitude, studying only the "local" atmosphere with no surface science. A more ambitious option is to perform surface science from "afar", observing in IR from altitude, but here there's a tangle of tradeoffs as cooler temperatures keep the aerobot in the clouds. Operating below the clouds, for better surface visibility, means higher temperatures. The clouds themselves entail a harsh chemical environment. And altitude control entails engineering complexity with added mass and points of failure.

There are a variety of possible aerobot missions at Venus, but there isn't going to be a be-all end all option that can visit the surface multiple times anytime soon.

Airplanes create other options, with some of the same tradeoffs. One possibility, unique to Venus, is an airplane that would operate in perpetual sunlight, flying east against the atmosphere's rotation, as the planet rotates beneath it. The clouds, again, create the unfortunate tradeoff: You get solar radiation for solar power or a view of the surface, but not both.

Posted by: antipode Feb 17 2021, 08:36 AM

Here's another Venus mission proposal from LPSC 21 that uses a long tether on a spool of some sort.

https://www.hou.usra.edu/meetings/lpsc2021/pdf/1425.pdf

While I love these designs are they doable? - we are talking about tethers 10s of km long,
being unrolled across zones with radically different temperatures and possible wind shear. I believe
wind speeds are expected to be low, but as pressures are so high....?

Would anyone like to comment on how feasible this is?

P

Posted by: stevesliva Feb 17 2021, 01:55 PM

That would be quite a lot of tether mass. It also doesn't mention if it's a gas balloon... does that go without saying?

Posted by: vjkane Feb 17 2021, 03:39 PM

From the abstract: "Current estimates for tow-body mass, incorporating the phase-change material, rechargeable battery power, pressure/temperature sensors, airspeed sensor, accelerometer, the near-infrared imager and a topmounted CCD camera for balloon and sky/cloud viewing on deployment and retraction, is ~2-3 kg. The tether, comprised of high-strength tensile fibers, a Gbspeed optical comm link, and a protective coating for the abrasive atmosphere, is planned to extend ~ 9 km to account for its downwind drift in the prevailing relative wind. The estimated tether mass is 3.6 kg, while the deployment/retraction system on the balloon gondola has an estimated mass of ~ 1 kg. "

Posted by: bobik Feb 21 2021, 04:57 PM

The https://sites.lesia.obspm.fr/envision/2021/02/18/assessment-study-report-complete/ is now out! Selection between https://sci.esa.int/web/cosmic-vision/-/theseus-assessment-study-report-yellow-book and https://sci.esa.int/web/cosmic-vision/-/envision-assessment-study-report-yellow-book not earlier than June 2021.

Posted by: JRehling Feb 21 2021, 05:24 PM

I missed, until now, the announcement made in October 2020, that the SPICA mission had been dropped from consideration for M5, making it now a decision between EnVision and Theseus.

Venus now has two candidate missions in a competition that will choose up to two out of four, and another competition in which Venus has one out of two. If the Discovery program indeed chooses two, then the only way Venus will fail to get at least one upcoming mission is for the decision process to rank those respective candidates in literally the one most unfortunate way possible. If all those options were equiprobable, then we have an 83% probability that Venus is about to garner its first dedicated mission with a focus on the surface of Venus since Magellan launched in 1989! The Discovery selection timelines was at least notionally supposed to conclude this month, which means we may be hearing next week.

Posted by: vjkane Feb 21 2021, 06:57 PM

To be somewhat more precise, 83% of possible combinations of mission selections would include at least one Venus mission. However, past selections have shown a low priority for Venus mission selection: 0 out of 4 in the last Discovery selection and the Venus radar mission (a heftier version of VERITAS) wasn't included as a New Frontiers finalist despite statements that it was ranked as a category 1 proposal in the reviews.

What I find intriguing is that NASA has pushed back the announcement of the selection of new Discovery missions to June, which is when the M5 selection is expected to be announced. EnVision apparently requires a NASA-provided radar system to fit within its budget. NASA and ESA could announce the selection of EnVision under the M5 program as a joint mission and then NASA selects two missions from DAVINCI+, Trident, and IVO. The downside for radar mapping of Venus in this scenario is that EnVision wouldn't begin its regular operations until ~2034, ~7 years after VERITAS would.

As a side note, there's an LPSC abstract on the Venus Emissivity Mapper instrument that all but states that the single band emissivity mapping of the surface that DAVINCI+ would do would not be able to definitively distinguish key surface compositions. (VEM would have several bands, and is included in both the VERITAS and EnVision proposals.) I suspect that the DAVINCI+ proposal argues otherwise. However, DAVINCI+ would examine limited, but high priority, areas on Venus where VEM, I believe, would map the entire planet.

Posted by: JRehling Feb 21 2021, 09:06 PM

Thanks for the updates, Van, although I quietly grumble over having to wait longer.

There is certainly the potential for interaction between the ESA and NASA selections, whether or not the various agencies allow for that interaction to occur.

The extent of the capability of emissivity mapping to distinguish surface units on Venus is one of those things where we can't know until we try; Venus itself will have to answer that question. EnVision/VERITAS on the one hand and DAVINCI+ are likely complementary and I'd be thrilled to see both fly. EnVision has a more complex radar system than VERITAS, so all else being the same, EnVision might make VERITAS' incremental contributions considerably lesser than EnVision alone. Point taken, though, that VERITAS would occur first.

Posted by: vjkane Feb 21 2021, 09:11 PM

I believe that the EnVision team has firmly stated that they can't fit into their budget without a NASA-supplied radar instrument (perhaps this has changed in the last year or so?), and NASA agreed to study supplying it.

If this is true, and if EnVision is selected, then the radar instrument they've been discussing likely won't be the one they would be flying.

Posted by: Phil Stooke Jun 2 2021, 07:40 PM

DAVINCI+ and Veritas, both selected - big times for Venus after a long hiatus!

Phil

Posted by: Explorer1 Jun 2 2021, 08:14 PM

Wonderful news!

Press release here: https://www.nasa.gov/press-release/nasa-selects-2-missions-to-study-lost-habitable-world-of-venus

Interesting:

.

Posted by: JRehling Jun 2 2021, 08:28 PM

I'm shivering in excitement. Congratulations to everyone who has a part in these missions. My gosh, the U.S. has only launched one mission dedicated to Venus in decades. It's about time!

Posted by: Holder of the Two Leashes Jun 2 2021, 10:03 PM

YYYYYEEEEEEEEEEESSSSS!

Posted by: TrappistPlanets Jun 2 2021, 10:35 PM

OH HECK YEAH!!

Posted by: Explorer1 Jun 2 2021, 11:22 PM

The PIs of both missions will be speaking tomorrow in this media event:
https://www.youtube.com/watch?v=EmWQiq-tAy4

Posted by: dtolman Jun 3 2021, 12:55 AM

Wow! Does both being selected mean that they are going to be combined somehow - or will they run as completely separate missions/probes. as if the other hadn't been selected?

Posted by: Phil Stooke Jun 3 2021, 01:05 AM

They are totally different, they can't really be combined. Rather, they are complementary.

Phil

Posted by: rlorenz Jun 3 2021, 02:18 AM

Venus missions like London buses, you wait for ages then two come along at once.....

I've been associated with the GSFC team since about 2008, when we proposed a probe+radar Venus Reconnaissance Orbiter, then VISAx (the probe alone, to Discovery in 2010), then DAVINCI (probe alone, to Discovery in 2015, went through Phase A [with VERITAS] through 2016 but Psyche/Lucy got selected instead), then proposed to New Frontiers as VICI, and then DAVINCI+..... so fifth time's a charm..... so there is a lot of sweat and tears behind every mission that eventually gets selected...

I lead the Atmospheric Structure Investigation and trajectory reconstruction effort on DAVINCI+ (pressure/temperature, plus gyros/accelerometers for upper atmosphere and documentation of entry dynamics, and Doppler tracking via the APL-supplied radio system)

It's great that the long-overdue high-resolution radar mapping of Venus will happen with VERITAS too (Magellan's stated goal was to map Venus as well as Mariner 9 mapped Mars.....). I have some mixed feelings, having played a major role in RAVEN, a Discovery radar mapper proposal in 2015 competing against VERITAS, but VERITAS will do a good job and be very complementary to DAVINCI+.

Obviously both missions were proposed in isolation, DAVINCI+ doesnt need VERITAS to determine a target location. But there will certainly be some scientific synergies that will emerge...

Posted by: JRehling Jun 3 2021, 03:14 AM

And in a sense, there were three Venus winners, because CUVIS, a high resolution UV spectrometer, was chosen to fly along with DAVINCI+. (A high precision clock will fly along with VERITAS, but that isn't Venus-related.)

One multi-synergy between the missions will occur at the DAVINCI+ landing site, which will be imaged in three or four different ways – radar imagery, radar altimetry, IR emissivity, and near-IR imagery from below the clouds. It seems as though the DAVINCI+ orbital/flyby imager, VISOR, will also possibly provide IR emissivity data that is complementary to VERITAS in selected regions such as Ishtar.

One of the added perks of Venus as a double target is that the cruise phase of the mission will be shorter than for any other planetary target. Both missions should have given us most/all of their science within a decade from the current time.

Posted by: Tom Tamlyn Jun 3 2021, 03:31 AM

From Scott Maxwell (@marsroverdriver) on twitter:

https://twitter.com/marsroverdriver/status/1400274744524509189

I look forward to reading Emily Lakdawalla's comments when she returns from vacation.

Posted by: dtolman Jun 3 2021, 03:46 AM

What will the descent probe's velocity be? Is it expected to be destroyed on contact with the terrain, or is there some outside chance of it surviving descent to give us some cock-eyed shots for a few minutes before the battery or other equipment succumbs to the environment?

Posted by: Hungry4info Jun 3 2021, 05:00 AM

From https://ntrs.nasa.gov/citations/20170002022.

Posted by: antipode Jun 3 2021, 08:03 AM

That's excellent. Lets hope against hope for at least 30 minutes then.

Maybe a shot or two from the surface a la Huygens?

P

Posted by: JRehling Jun 3 2021, 08:37 AM

Reading up on the science of noble gas abundance in planetary reservoirs, I gained a newfound appreciation of why we need vastly better measurements than had previously been made at Venus.

While there is often an interesting story to be interpreted regarding the ratio of the top two or three isotopes, the full picture is much more complex, and to take the most challenging case, xenon has nine isotopes that are (basically) stable [seven truly stable, and two have extremely long half-lives]. In Earth's atmosphere, xenon abundance is 87 parts per billion, so the individual isotopes are, obviously, in some cases more than 9x less abundant than that. To measure their abundance with even one significant digit means measuring atmospheric components to better than 1 part per billion, and ideally even several times more accurate than that.

To date, 1970s-era instruments have returned the best data, and those placed only loose constraints on the abundance of xenon in Venus's atmosphere. Basically, good data for krypton and xenon don't exist at all.

Now, if this seems arcane, here's the stunner – we are still searching for an explanation for the unexpectedly low xenon abundance in Earth's atmosphere! (When we don't understand something about Earth, that's a strong sign that we don't understand it for planets in general.) In matters of noble gas abundance, Earth is just one case, with Mars, the solar wind, Jupiter, and meteorites being other cases. And so, Venus is potentially a very important case for understanding not merely the evolution of the atmosphere of Venus, but even of Earth… and, we can be sure, for understanding terrestrial exoplanets outside our solar system.

For what it's worth, Titan is apparently another beast altogether, due to the physical chemistry of ices and noble gases although ice has been at least discussed as a possible reservoir for Earth's "missing" xenon.

So, the atmospheric composition instruments on DAVINCI+ may lead to realizations of extremely broad reach, even so far as the history of Earth is concerned.

Posted by: vjkane Jun 3 2021, 02:30 PM

D+'s camera points down. So if the probe survives landing, there will be pictures of the camera pressed against the surface.

Posted by: rlorenz Jun 3 2021, 03:02 PM

Of the 4 Pioneer Venus probes, which had a similar design posture to impact survival (as did Huygens), signals from 2 were lost immediately at impact, signals from one for a second or two (consistent, perhaps with toppling over and pointing the antenna away from Earth) without any real science content, and signals from one were received for an hour, showing some variation in light levels.

So the empirical odds are about 25% that we get something from the surface.

I suppose the ideal for DAVINCI would be to topple over in such a way that the camera points at the horizon, and the antenna happens to point at the right azimuth to maintain the data relay. Whether the camera lens is scratched up or dusty is another story. We'll at least be running the accelerometers to see if the microseisms indicated by Venera are seen, those measurements don't require any orientation except for radio link

But this would all be gravy, the descent imaging should be spectacular.

Posted by: vjkane Jun 3 2021, 06:21 PM

Ralph, are you on the DAVINCI+ team? If so, congratulations!

I'm hoping that the D+ team releases a video of equivalent descent imaging over a terrestrial location to give us a preview of the types of images expected. If I remember correctly, the images will have overlap, and the team will build photogrammetric 3D models of the surface.

If the probe does fall over, I wonder if the images would be useful. I expect that the camera will be designed to focus a few meters to infinity.

Posted by: JRehling Jun 3 2021, 06:31 PM

I for one was just looking at MARDI descent imagery to get an idea of the kind of imagery we might see on Venus. I'm expressing a hunch that some unsharp mask processing will be part of the fun.

Any luck with a putative sideways image and focus distance will pertain to additional luck of how the probe landed and the local slope. Tessera terrain is rough. It seems like with rough terrain you're somewhat likely to be looking at the sky or staring right into something point-blank. But this is all wrapped in many unknowns.

And indeed, congrats Ralph and Mike, who have a hand in these successes.

Posted by: vjkane Jun 3 2021, 06:45 PM

The last data may show the probe bouncing down a steep slope...

Posted by: vjkane Jun 3 2021, 06:52 PM

Perhaps the most valuable landed science simply would be additional atmospheric analyses.

Posted by: JRehling Jun 3 2021, 09:30 PM

I believe that the noble gas analyses will be the same near the surface as at the surface, but more time will mean lowered error bars, which is a good thing.

For other gases, there's the potential of surface/atmosphere chemistry or physical chemistry which is the sort of thing that might be more about specifically Venus than anything cosmic, but also exciting in its own right, for sure. Sometimes interesting things happen in that last meter.

As a reminder, Pioneer Venus suffered a failure in multiple systems on all probes at an altitude of 12.5 km, quite a long way from that last meter.

Posted by: rlorenz Jun 4 2021, 02:58 AM

(See post 283)

IIRC Jim Garvin got some imaging from a helicopter as an analog to trial/showcase the photogrammetry and trajectory reconstruction. But MARDI / EDLCAMs are pretty good analogs, I suspect

Posted by: Saturns Moon Titan Jun 10 2021, 09:46 AM

Rumor has it ESA will announce its M5 mission selection today, choosing between Theseus and EnVision. Godspeed EnVision! Three Venus missions would be amazing...

Posted by: Bjorn Jonsson Jun 10 2021, 10:41 AM

EnVision selected!

Exciting times ahead for everyone interested in Venus. The launch of EnVision doesn't occur until ~2032 though.

Posted by: JRehling Jun 10 2021, 11:22 AM

Unbelievable! Venus sweeps three mission selections - four if you remember the CUVIS ride-along.

EnVision is a bit similar to Veritas, but many details set them apart. EnVision's VenSpec-M instrument and the VEM emissivity instrument on Veritas appear to be precisely the same instrument from the same provider under different names.

EnVision's suite of spectrometers is described here:
https://ui.adsabs.harvard.edu/abs/2019EGUGA..21.8665H/abstract

It will be interesting to compare data from EnVision's VenSpec-U ultraviolet spectrometer and CUVIS, which will fly on DAVINCI+. Together, the pair will provide far better data on the unknown ultraviolet absorber than presently exists. It remains to see if spectroscopy is capable of uniquely determining the nature of the ultraviolet absorber, but if so, these two separate investigations would be the best imaginable effort to do so.

While EnVision includes a subsurface radar instrument that Veritas does not, their main SAR instruments are also different in focus from one another. Veritas will launch first and map globally X-band (about 3 cm) while EnVision will map about 20% of the planet (most areas that are rough and high altitude) in S-band (about 10 cm) with higher spatial resolution. The map here suggests that Alpha Regio, the landing site of DAVINCI+'s probe might not be covered by EnVision's radar mapping, but perhaps that is subject to change:

https://sci.esa.int/documents/34923/36148/1567260369382-EnVision_CDF_IFP_2018_Summary.pdf