Between 1966 and 1985, several probes, mostly of Soviet design, successfully landed on Venus. Many of them continued operating long enough to send back audio, images, and various measurements, though none survived for longer than about two hours.

Given what we know about Venus's atmosphere, including the tremendously high temperature and pressure, what would the probes that made a soft landing look like today if we could see them up close? Would they appear more or less intact, or crumpled like a crushed tin can, or even partly melted like Salvador Dalí's drooping clocks? Would the surfaces show any signs of dust, abrasion, or oxidation?

For reference, there exist various photos of replicas of the Venus landers as well as artists' impressions of the landers on the Venusian surface. (I don't embed these images here as I can't find any good ones that are freely licensed.)

Also note that while an earlier question here about Venus treats the topic of landers getting crushed by atmospheric pressure, its time frame is limited to the exact point when the lander fails. My question is more about what happens to the lander in the long term, after many decades of neglect.

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    $\begingroup$ Given how corrosive the atmosphere is the question may be if there's anything left at all. $\endgroup$ – GdD Sep 21 '20 at 13:28
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    $\begingroup$ @GdD - well, at least some parts can be chemically durable. For example titanium and glass are chemically inert, at least at ambient temperarures. But I'm not sure it's the same at Venus temperatures about +470 °C... $\endgroup$ – Heopps Sep 21 '20 at 14:01
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    $\begingroup$ It's an interesting question and I hope there's an informed answer to it @Heopps $\endgroup$ – GdD Sep 21 '20 at 14:01
  • $\begingroup$ Unless the probes contained some airtight compartments, they would not be crushed by Venus's atmosphere. Space probes are usually open structures so the pressure is acting on all sides of all the solid components that make up the probe. These are largely incompressible so there should be no crushing. $\endgroup$ – Oscar Bravo Sep 22 '20 at 9:51
  • $\begingroup$ The sulfuric acid doesn't survive to the surface. At those temperatures it dissociates to SO3 and H2O. SO3 is a powerful oxidizer but its concentration is very low, so oxidation of spacecraft materials would be slow. But there is supercritical CO2, which attacks non-metals such as wire insulation and non-metal gaskets rapidly. Many probe components, especially some electronics, can't handle high pressures and were protected in reverse-pressure vessels. Designed for a fairly short mission, those would probably leak to a relatively small delta-pressure before they would collapse. $\endgroup$ – Tom Spilker Sep 23 '20 at 5:34

Let's talk about the major materials that made up the Venera landers. https://space.stackexchange.com/a/9965/25 has a great summary of what the landers were made of, they are composed of include Titanium, gold, fiberglass, KG-25 an high-temperature polyurethane foam, and PTKV-260. There are a bunch of other materials, likely including some glass and other things that have the potential, but a complete list of materials isn't available. Most of those wouldn't work.

The titanium already showed signs of oxidation when the probes were working. It is safe to assume that continued. Gold does not oxidize and should have remained. Any fluids and foams would have likely dissolved, just not leaving much. Aluminum likely remained mostly intact, although weakened somewhat through some extra oxidation, it has probably collapsed. It will eventually succumb to the sulfuric acid. Iron will have dissolved in any sulfuric acid that makes it to the surface.

This paper suggests gold, iridium, silicon dioxide, aluminum nitride, silicon nitride, and aluminum oxide are all good materials to use on Venus. I can't find any reference to any of these being used except for gold, and most likely silicon dioxide. Any of these materials would have survived. Most of the rest would be some kind of oxidized mess, although I do suspect that most of it would at least remain close. There is a slight surface wind on Venus which would have blown away the really badly damaged components, but much of them would have only been oxidized versions of what was already there.

Any parts that did survive would be covered in dust, due to the wind. The images we have seen of the surface of Venus show very few rocks, and most of those are pretty small. It is likely that any light wires would have been blown around, along with the severely degraded components. The glass from lenses would have likely remained, along with at least a part of the electronics, but would probably be covered in dust.

Some of the later missions made use of special materials, which probably helped them survive more intact. I can't find any details, but they seem mostly to have been used for the electronics. Aluminum and even iron will last long enough to serve its purpose on Venus, and the limiting factor never was keeping the structure together.

Bottom line, very little is likely left, and what is left would be scattered and covered in dust.

  • $\begingroup$ Did these have some primary structural material i.e. steel, aluminum/magnesium, that comprised most of its dry weight, something that held the spacecraft together that other things were connected to? Venera dry masses were about 400 kg to 700 kg. Much of that will not be Titanium, gold, fiberglass, KG-25 an high-temperature polyurethane foam, and PTKV-260 or glass. Since it will react with something, oxidize or whatever, if anything it's going to be even heavier now. For example 1 kg of aluminum is almost 2 kg of Al2O3. $\endgroup$ – uhoh Sep 21 '20 at 18:15
  • $\begingroup$ What does 500 or 1000 kg of "dust" look like? Is it scattered by wind? Is there much wind right at the surface, or is it in fact pretty calm? $\endgroup$ – uhoh Sep 21 '20 at 18:16
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    $\begingroup$ Added details about aluminum and steel, one of which most likely made the bulk of the spacecraft structure. They wouldn't survive well. There isn't much wind on the surface, but the wind will be quite powerful with such a thick atmosphere. $\endgroup$ – PearsonArtPhoto Sep 21 '20 at 19:15
  • $\begingroup$ yep, but it's not like it landed in a puddle of liquid sulfuric acid that was then poured down the drain and disappeared; the surface looks dry; the acid is in droplets. I'm still trying to imagine where hundreds of kilograms of structural metal actually goes. Does it dissolve into fog droplets and get blown away as an aerosol, or drip to the ground and get deposited as some aluminum or iron salt, then get blown away, or is there a pile of rust-like stuff. I don't mean that that has to be part of an answer, it's just fun to think about. I can use anything, anything to procrastinate :-) $\endgroup$ – uhoh Sep 21 '20 at 22:48
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    $\begingroup$ I would love to have a better answer myself. This proper would be the work of journal level articles, and I think it would be interesting. But a pile of rusted metal with some interesting thing sticking out, covered in sand is about the best short of that I think we are likely to get. $\endgroup$ – PearsonArtPhoto Sep 21 '20 at 23:05

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