IPB

Welcome Guest ( Log In | Register )

Future Venus Missions
Phil Stooke
post Jul 1 2005, 01:30 AM
Post #1


Senior Member
****

Group: Members
Posts: 5761
Joined: 5-April 05
From: Canada
Member No.: 227



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


--------------------
... because the Solar System ain't gonna map itself.
Go to the top of the page
 
+Quote Post
 
Start new topic
Replies
Guest_BruceMoomaw_*
post May 3 2006, 02:51 PM
Post #2





Guests






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/Chap...ummaryVEXAG.pdf ).

Also see Emily's series of very useful blog entries on the goings-on at VEXAG ( http://planetary.org/blog/ ).
Go to the top of the page
 
+Quote Post
nprev
post May 5 2006, 12:40 AM
Post #3


Senior Member
****

Group: Moderator
Posts: 7102
Joined: 8-December 05
From: Los Angeles
Member No.: 602



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

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... blink.gif


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
Guest_BruceMoomaw_*
post May 6 2006, 09:22 AM
Post #4





Guests






QUOTE (nprev @ May 5 2006, 12:40 AM) *
Mr. Esposito's presentation was indeed informative, Bruce; thanks for posting the link! smile.gif

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... blink.gif


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.
Go to the top of the page
 
+Quote Post
PhilHorzempa
post May 7 2006, 04:39 AM
Post #5


Member
***

Group: Members
Posts: 164
Joined: 17-March 06
Member No.: 709



QUOTE (BruceMoomaw @ May 6 2006, 05:22 AM) *
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.



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
Go to the top of the page
 
+Quote Post

Posts in this topic
- Phil Stooke   Future Venus Missions   Jul 1 2005, 01:30 AM
- - BruceMoomaw   Well, to repeat a point I've suggested (somewh...   Jul 1 2005, 09:23 AM
|- - JRehling   Phil is, of course, completely right about the lis...   Jul 1 2005, 04:28 PM
|- - JRehling   QUOTE (JRehling @ Jul 1 2005, 08:28 AM)A poss...   Dec 15 2005, 01:34 PM
|- - Jeff7   QUOTE (JRehling @ Dec 15 2005, 08:34 AM)A bit...   Dec 15 2005, 06:33 PM
|- - JRehling   QUOTE (Jeff7 @ Dec 15 2005, 10:33 AM)I suppos...   Dec 15 2005, 09:21 PM
|- - Bob Shaw   A simple explanation for at least part of the stor...   Dec 15 2005, 11:38 PM
|- - JRehling   QUOTE (Bob Shaw @ Dec 15 2005, 03:38 PM)A sim...   Dec 16 2005, 02:17 AM
- - BruceMoomaw   I see I forgot to provide the URL for the LPSC abs...   Jul 1 2005, 09:27 AM
|- - Myran   QUOTE (BruceMoomaw wrote.)....and without any need...   Jul 1 2005, 04:31 PM
- - BruceMoomaw   The main justification for simplifying a Venus lan...   Jul 1 2005, 11:28 PM
|- - AndyG   Given that the surface is so hot and so highly pre...   Jul 7 2005, 02:39 PM
|- - Bob Shaw   As there are some fairly well-described outline de...   Jul 7 2005, 02:54 PM
|- - JRehling   QUOTE (Bob Shaw @ Jul 7 2005, 07:54 AM)As the...   Jul 7 2005, 08:18 PM
- - BruceMoomaw   Actually, this type of mission -- a balloon using...   Jul 8 2005, 01:58 AM
|- - Bob Shaw   Bruce: Very interesting - you are a fount of know...   Jul 8 2005, 02:47 PM
|- - Bob Shaw   Among the interesting points in the .PDFs to which...   Jul 8 2005, 03:03 PM
||- - Bob Shaw   A conceptual small Venus atmosphere probe picture ...   Jul 20 2005, 01:45 PM
|- - gndonald   QUOTE (Bob Shaw @ Jul 8 2005, 10:47 PM) S...   Feb 20 2006, 04:34 PM
- - remcook   ESA is looking at a mission that is using a balloo...   Jul 20 2005, 01:53 PM
- - BruceMoomaw   NASA's Venus Exploration Analysis Group (VEXAG...   Nov 6 2005, 02:15 AM
|- - JRehling   QUOTE (BruceMoomaw @ Nov 5 2005, 07:15 PM)the...   Nov 6 2005, 06:29 AM
- - remcook   a good update from emily on oncoming missions (VEX...   Nov 9 2005, 10:01 AM
- - BruceMoomaw   To my delight, last night I stumbled by chance acr...   Nov 24 2005, 03:23 PM
|- - JRehling   QUOTE (BruceMoomaw @ Nov 24 2005, 07:23 AM)On...   Nov 25 2005, 05:22 PM
- - BruceMoomaw   One other thing which I just now noticed on the la...   Nov 24 2005, 03:26 PM
- - Phil Stooke   I just tried to access the Venus lander PDS file B...   Nov 24 2005, 04:10 PM
- - BruceMoomaw   It just came through OK for me again (using the UR...   Nov 24 2005, 10:10 PM
|- - vjkane2000   QUOTE (BruceMoomaw @ Nov 24 2005, 03:10 PM)On...   Nov 26 2005, 06:31 AM
- - Phil Stooke   You're right, Bruce... tried a different machi...   Nov 25 2005, 02:22 PM
- - BruceMoomaw   Remember Magellan, which completed 1.5 orbits arou...   Nov 26 2005, 02:27 AM
- - BruceMoomaw   This wouldn't make the SAGE landers that much ...   Nov 26 2005, 08:24 AM
|- - vjkane2000   QUOTE (BruceMoomaw @ Nov 26 2005, 01:24 AM)Th...   Nov 27 2005, 06:08 AM
|- - JRehling   QUOTE (BruceMoomaw @ Nov 26 2005, 12:24 AM)Th...   Nov 27 2005, 07:13 AM
- - edstrick   I'd be really interested in knowing the calcul...   Nov 27 2005, 09:51 AM
- - BruceMoomaw   First: it's not the WEIGHT of imaging cameras ...   Nov 27 2005, 09:55 AM
- - Phil Stooke   Bruce said: "One possibility that comes to m...   Nov 27 2005, 09:32 PM
|- - tedstryk   Another possibility is, if the probe transmits at ...   Nov 28 2005, 03:01 AM
|- - vjkane2000   QUOTE (tedstryk @ Nov 27 2005, 08:01 PM)Anoth...   Nov 28 2005, 03:34 AM
- - BruceMoomaw   But, once again, a high-resolution radar orbiter -...   Nov 28 2005, 02:09 AM
- - Phil Stooke   Bruce, yes, lots of tesserae have small ponds of l...   Nov 28 2005, 03:34 AM
- - edstrick   The frustration of understanding anything about th...   Nov 28 2005, 06:16 AM
- - RNeuhaus   Why does not do design a good space architecture a...   Nov 28 2005, 03:20 PM
|- - JRehling   QUOTE (RNeuhaus @ Nov 28 2005, 07:20 AM)Why d...   Nov 28 2005, 04:51 PM
|- - RNeuhaus   QUOTE (JRehling @ Nov 28 2005, 11:51 AM)An or...   Nov 28 2005, 08:42 PM
- - BruceMoomaw   I take for granted that the first three or four ge...   Nov 29 2005, 01:16 AM
- - djellison   Ahh - Nico and I saw a presentation about that at ...   Dec 15 2005, 01:38 PM
- - BruceMoomaw   Yep. One would think that -- if the Ashen Light a...   Dec 16 2005, 03:17 AM
|- - David   QUOTE (BruceMoomaw @ Dec 16 2005, 03:17 AM)Ye...   Dec 16 2005, 01:48 PM
- - BruceMoomaw   Well, it's a fact that E.E. Barnard -- one of ...   Dec 16 2005, 11:27 PM
|- - Bob Shaw   There's an empirical test (for once), and that...   Dec 17 2005, 12:22 AM
|- - David   QUOTE (BruceMoomaw @ Dec 16 2005, 11:27 PM)We...   Dec 17 2005, 12:47 AM
|- - JRehling   QUOTE (BruceMoomaw @ Dec 16 2005, 03:27 PM)We...   Dec 17 2005, 06:28 AM
|- - ljk4-1   QUOTE (BruceMoomaw @ Dec 16 2005, 06:27 P...   Feb 21 2006, 10:20 PM
|- - Bob Shaw   QUOTE (ljk4-1 @ Feb 21 2006, 10:20 P...   Feb 21 2006, 10:54 PM
||- - DonPMitchell   Bob, what in particular did you want to know about...   May 4 2006, 08:33 PM
||- - Bob Shaw   QUOTE (DonPMitchell @ May 4 2006, 09:33 P...   May 7 2006, 03:51 PM
||- - DonPMitchell   QUOTE (Bob Shaw @ May 7 2006, 08:51 AM) D...   May 7 2006, 05:37 PM
||- - Bob Shaw   Don: Thanks! I hadn't previously realise...   May 7 2006, 06:02 PM
||- - DonPMitchell   QUOTE (Bob Shaw @ May 7 2006, 11:02 AM) D...   May 7 2006, 06:10 PM
||- - Bob Shaw   QUOTE (DonPMitchell @ May 7 2006, 07:10 P...   May 7 2006, 06:14 PM
||- - DonPMitchell   QUOTE (Bob Shaw @ May 7 2006, 11:14 AM) C...   May 7 2006, 07:13 PM
||- - mchan   Over mine, too. IJFGI. Learn something new every...   May 8 2006, 12:52 AM
||- - Bob Shaw   QUOTE (mchan @ May 8 2006, 01:52 AM) Over...   May 8 2006, 09:07 PM
|- - JRehling   QUOTE (ljk4-1 @ Feb 21 2006, 02:20 P...   Feb 21 2006, 11:56 PM
- - dvandorn   One reason Martian craters are hard to see from Ea...   Dec 17 2005, 01:39 AM
- - Phil Stooke   I think the whole issue of earth-based identificat...   Dec 17 2005, 05:21 AM
|- - Bob Shaw   QUOTE (Phil Stooke @ Dec 17 2005, 05:21 A...   Feb 20 2006, 10:11 PM
- - edstrick   There was a full set of preliminary science papers...   Feb 22 2006, 08:37 AM
- - Phil Stooke   Replying to Bob about seeing Aristarchus with his ...   Feb 22 2006, 01:34 PM
- - BruceMoomaw   The presentations from the second VEXAG meeting ha...   May 3 2006, 02:51 PM
|- - nprev   Mr. Esposito's presentation was indeed informa...   May 5 2006, 12:40 AM
|- - DonPMitchell   QUOTE (nprev @ May 4 2006, 05:40 PM) Mr. ...   May 5 2006, 01:53 AM
|- - BruceMoomaw   QUOTE (nprev @ May 5 2006, 12:40 AM) Mr. ...   May 6 2006, 09:22 AM
|- - PhilHorzempa   QUOTE (BruceMoomaw @ May 6 2006, 05:22 AM...   May 7 2006, 04:39 AM
||- - DonPMitchell   QUOTE (PhilHorzempa @ May 6 2006, 09:39 P...   May 8 2006, 09:08 AM
|- - tty   QUOTE (BruceMoomaw @ May 6 2006, 11:22 AM...   May 7 2006, 06:00 PM
|- - BruceMoomaw   QUOTE (tty @ May 7 2006, 06:00 PM) Plate ...   May 8 2006, 01:39 AM
- - RNeuhaus   I feel that the last proposal from VEXAG is more s...   May 3 2006, 04:01 PM
- - Phil Stooke   Hi Don! That was quick! Phil   May 4 2006, 09:00 PM
- - BruceMoomaw   Aha! I always wondered why Madame de Pompadou...   May 8 2006, 10:09 PM
|- - Bob Shaw   QUOTE (BruceMoomaw @ May 8 2006, 11:09 PM...   May 8 2006, 10:40 PM
|- - Chmee   QUOTE (Bob Shaw @ May 8 2006, 06:40 PM) B...   May 9 2006, 04:28 PM
|- - ljk4-1   QUOTE (Chmee @ May 9 2006, 12:28 PM) So w...   May 9 2006, 05:56 PM
|- - Bob Shaw   QUOTE (Chmee @ May 9 2006, 05:28 PM) So w...   May 9 2006, 05:56 PM
- - BruceMoomaw   After clawing my way through my CD-ROM library of ...   May 12 2006, 08:08 AM
- - vjkane   Presentations from the last VEXAG meeting are now ...   Jul 23 2008, 03:48 PM
- - Vultur   I think Venus rovers and balloons, someday, might ...   Nov 15 2008, 07:49 PM
- - Enceladus75   Whilst it would be brilliant to have rovers on Ven...   Nov 19 2008, 07:58 PM
- - PhilCo126   Venus resembles a depiction of "Hell" so...   Nov 20 2008, 07:04 PM
- - Juramike   The Venera landers did manage last about an hour o...   Nov 20 2008, 08:35 PM
|- - vjkane   QUOTE (Juramike @ Nov 20 2008, 08:35 PM) ...   Nov 21 2008, 05:31 PM
|- - huygens_stowaway   QUOTE (vjkane @ Nov 21 2008, 05:31 PM) Th...   Dec 4 2008, 09:37 PM
|- - centsworth_II   QUOTE (huygens_stowaway @ Dec 4 2008, 04...   Dec 4 2008, 10:02 PM
- - Paolo   An interesting Venus Flagship Mission Study   Jul 12 2009, 03:01 PM
- - qraal   Hi Guys Geoff Landis discusses aerobots and surfa...   Jul 16 2009, 09:34 AM
|- - MahFL   The Landis paper is really interesting, I did not ...   Jul 16 2009, 12:35 PM
|- - stevesliva   QUOTE (MahFL @ Jul 16 2009, 08:35 AM) The...   Jul 16 2009, 03:52 PM
- - tasp   And recall, even with an electronic device operati...   Jul 16 2009, 11:25 PM
- - stevesliva   Yeah. One of the reports mentioned that resistors...   Jul 16 2009, 11:39 PM
2 Pages V   1 2 >


Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 1st November 2014 - 07:39 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.