Russia Plans "long-lived" Venus Probe Options

[Waspie_Dwarf]

Russia Plans "Long-Lived" Venus Probe

The press secretary of the Russian Federal Space Agency, Vyacheslav Davidenko, has said that Russia will design and launch a long-living probe to Venus by 2015. The probe is known as Venera-D.

Davidenko told a news briefing that within the federal Space budget for 2006-2015 was envisaged, “work to develop a principally new spacecraft, Venera D, intended for detailed studies of the atmosphere and surface of Venus”.

“It is expected that the craft with a long, more than one month period of active existence will land on the surface of the planet that is the nearest to the earth. Nobody has done such thing on Venus so far.”

Source: ITAR-TASS

[Guest_BruceMoomaw_*]

God, what a flock of questions! Let me answer at least a few of them:

(1) Venus' atmosphere isn't nearly as dense as water -- but it IS dense enough that, as LJK said, the Soviet landers carried out all the final part of their deceleration just using a circular disk (not very wide) fastened to their upper end as a drag brake. (They touched down on a ring fastened to their by a bunch of shock-absorbing struts.)

(2) Venus penetrators are simply not worthwhile -- the surface, after all, is as hot as the atmosphere, and the slim shape of a penetrator makes it much harder to properly thermally insulate its contents.

(3) As for the corrosive atmosphere, there are some worries about that -- but the sulfuric acid in Venus' air is found only in the upper levels at the cloud layer (where its droplet density is actually quite sparse; as with Titan's smog, it's opaque from the outside only because the layer is so spatially thick). There clearly IS something chemically reactive in the trace gases in Venus' hot lower atmosphere, which caused the mysterious set of reactions that caused a large number of the sensors on all four of the Pioneer 13 probes to malfunction at (I believe) 8 km above the surface -- but what that something is we still don't know, despite an entire workshop devoted to the mystery two decades ago. Apparently some substance on the sensors -- probably their insulation -- actually reacted with some trace gas and caught on fire at that height, but we still have no idea just what the reaction actually was, or why the Soviets had no such problem.

(4) The idea of using tiny vacuum tubes on Venus electronics has actually been floated since the late 1970s. But the whole problem of temperature is still huge. On pg. 25-26 of the Solar System Strategic Roadmap report ( http://www.hq.nasa.gov/office/apio/pdf/sol...lar_roadmap.pdf ) -- which was described at the COMPLEX meeting as still mostly valid -- it's noted that we have electronics that can operate at 300 deg C (not 250, as I stated earlier), but we still need 200 degrees higher. Also: "Not all electronic components can or should be implemented in high temperature components. Communications and power electronics have the most payoff. Digital electronics, which have low power dissipation, are best implemented in conventional electronics by using active thermal control." The idea of running the active cooler with a mechanical drive that utilizes the large amount of waste heat from an RTG is mentioned (as a necessity) on pg. 22. For this reason by itself, an RTG seems to be a necessity on any long-lived Venus lander. (A Venus rover that would use just such a system is described at http://www.agu.org/cgi-bin/SFgate/SFgate?&...t;P54A-06" -- although, once again, wheels seem less practical for Venus exploration than an active buoyancy system, utilizing a small steel bellows balloon as described by Victor Kerzhanovich, which allows the rover to glide along just a few meters above the surface and touch down periodicially for sampling.)

(5) As for electric power, I've seen both RTGs and temperature-resistant solar cells mentioned as possibilities (the latter for the bobbing Venus Geoscience Aerobot). There is actually quite a lot of sunlight on Venus' surface -- even given the blocking of sunlight by the cloud layer, it's about half as bright on the Venusian surface as it is on Earth. But another possibility for the VGA is a simple vertical windmill fastened to the gondola, utilizing the flow of dense air past the gondola during descent and ascent to run a generator recharging onboard batteries.

(6) As for the scientific goals of long-lived Venus landers, the Strategic Roadmap places great emphasis on the search for granite or sedimentary rocks that might indicate the presence of oceans on ancient Venus. It's a bit hard to see where we go from there, though. Just finding any sedimentary deposits on Venus that might be able to preserve fossils will be atrociously hard, let alone examining them for microbial or biochemical fossil evidence using in-situ instruments. (Especially since, I imagine, the heat alone will have been likely to break down complex organics even in the interiors of sedimentary rocks.) A sample-return mission would be mindbogglingly difficult and expensive -- the figure of $10 billion has been mentioned in the past, which means that there's an excellent chance that we won't have seen it by mid-century. And indeed the National Research Council, in its review of the Strategic Roadmaps ( http://www.nap.edu/books/0309099439/html/ ), indicates on pg. 18 that the Roadmap errs in describing such an astrobiological goal as the only important goal for Venus exploration -- which will be especially true if it turns out that the massive crustal recycling processes that seem to have occurred on Venus have totally destroyed any ancient crustal rocks. The only workable way to explore Venus would seem to be very incrementally -- checking cautiously with early missions to see if there's anything geologically interesting enough down there to be worth any near-future follow-ups with more technologically sophisticated and much more expensive later landers.

[Guest_Richard Trigaux_*]

God, what a flock of questions!  Let me answer at least a few of them:


(6)  As for the scientific goals of long-lived Venus landers, the Strategic Roadmap places great emphasis on the search for granite or sedimentary rocks that might indicate the presence of oceans on ancient Venus.  It's a bit hard to see where we go from there, though.  Just finding any sedimentary deposits on Venus that might be able to preserve fossils will be atrociously hard, let alone examining them for microbial or biochemical fossil evidence using in-situ instruments.  (Especially since, I imagine, the heat alone will have been likely to break down complex organics even in the interiors of sedimentary rocks.)  A sample-return mission would be mindbogglingly difficult and expensive -- the figure of $10 billion has been mentioned in the past, which means that there's an excellent chance that we won't have seen it by mid-century.  And indeed the National Research Council, in its review of the Strategic Roadmaps ( http://www.nap.edu/books/0309099439/html/ ), indicates on pg. 18 that the Roadmap errs in describing such an astrobiological goal as the only important goal for Venus exploration -- which will be especially true if it turns out that the massive crustal recycling processes that seem to have occurred on Venus have totally destroyed any ancient crustal rocks.  The only workable way to explore Venus would seem to be very incrementally -- checking cautiously with early missions to see if there's anything geologically interesting enough down there to be worth any near-future follow-ups with more technologically sophisticated and much more expensive later landers.

I think that, besides understanding formation and evolution of Venus, the search for past life (or at least past Earth like conditions) is the most interesting goal. If we find that Venus had granite or water, even a long time ago, that makes of it candidate n°1 for life in the solar system. Even finding a very ancient primitive fossil such as a stromatolith would be a breathtaking evidence, and the actual existence of life elsewhere than on Earth would have inhcredible philosphical/moral implications.


About the mountain ranges on Venus, I stated above that they could be continents like on Earth. But on Earth the surface and altitude of continents are the result of two opposite forces:
-plate tectonics which tends to gather and shrink the continents (small surface-high altitude)
-erosion by rain which tends to spread the continents and arase all what is above the ocean level (which makes flat continents, except where mountains are actually growing).

What happens on Venus could be a bit different, if a plate tectonics played alone and gathered small but high-altitude continents. If this is the case, it implies that there never was a large ocean. On the other hand, most theories of plate techtonics say it is driven by water on the surface, explaining why there is not on Venus. Anyway there could have be some running water on Venus before the today sulphuric acid cloud layer absorbs all the available water.

So, if the Venus mountains are really continents, they are certainly formed of granite and other light rocks, floating on a basaltic mantle (explaining why they keep their altitude despite softened rocks). This is the reason why searching for such rocks in continents is the N°1 geological objective (Some pancake volcanoes may be trachitic, a lava which is roughly molten granite).

To search for fossils at random is certainly hopeless. We need first a detailed geological map of all the mountains, in order to understand their formation and their detailed features.

For all these reason, I think that the geological exploration of Venus must begin with:

-A multi-frequencies high resolution several passes SAR radar mapping (low frequencies may have some penetration into rocks, allowing to better detect layering). This could be done with an orbiter, also using infrared cameras to probe the ground.

-A fleet of many small cheap aerobots, stabilized at an altitude just above the mountains. The main spaceship releases them in a timed sequence, on various trajectories, so that they enter the atmosphere and fly over mountain ranges, caried by high altitude winds. Their unique instrument would be a multispectral infrared imager, allowing to determine the composition of rocks in mountains and some other places of interest. They would be powered by batteries and cooled by a bottle of nitrogen, and last some hours or some days, so that we do not have to bother with new technologies. Some understanding of venusian winds are however required, and this is preciselly the main goal of Venus Express.

These aerobots may give an understanding of the geological structure of the venusian mountains, and give some hints of places to search for fossils, the later requiring to stay for long in the venusian inferno.

If they find that mountains are formed of basalt, we are all false.

About fossils themselves, we cannot expect to find organic materials, certainly decayed for long ago. Even limestone and shells cannot be expected, and sulphur chemistry is controversial. We shall certainly find no surface layer billions years old, even with the weak erosion on Venus. And continents may certainly have a heck of a geography, unpracticable on wheels and even on legs: most are formed of large folds, which reached and went beyong equilibrium slopes, forming cracks boulders and craggs everywhere. But, with a flying bot, this turns to be our chance: large sections of thick geological layers are available everywhere. This is why I suggested an aerobot musing vertically along cliffs, where it could examine closely the whole history of venusian sedimentary rocks (if there are some) in search of fossil traces: stromatholites, diatomites, vugs, worm paths and imprints in shales, etc.

The first instrument of this aerobot would be a radioactive datation system, and after a composition and crystallography lab. This would allow to understand the layer sequences. After, a large field microscopic imager with a shape detection software would allow to search for fossil traces, and send on Earth the most relevant among billions of images.

Eventually, if we find some unclear traces, the aerobot could end with the samples in a given rendez-vous place, holding the sample cannister ready for a further sample return mission. But, I think, if we do not find clear shapes, we shall no more find chemical traces, so that a sample return mission seems not very relevant for now.

A tip for a sample return mission would be to have the sample cannister raised up by a baloon, and sent in low orbit by a small rocket. The problem with a venusian sample return would be that, starting from the ground, we need a Earth-sized rocket, like a Soyouz, and working in a venusian environment, and all this after a several months travel, packing, unpacking, etc. Dreadful.