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Guilty pleasure: I just returned from one tinfoil-hat type of internet pages which suggests that we are being visited by Aliens who live on Venus. The fact, that we have only pictures from the ground from the seventies make it bit spooky (and argument for the site)

Anyway. Real question starts here. NASA proposed Rover mission for Venus and Wiki says it is currently proposed for year 2022

For scope of this question, suppose that NASA really launches rover mission to Venus in 2022 and that it is successful. Actually so successful, that it finds first "alien life" - to remove any tinfoil hats, I obviously mean life in form of bacteria.

Would it make more sense to shift humanity attention to Venus? Or would we continue Mars manned mission simply because "it is easier"?

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Going to Venus is not particularly difficult in general terms (indeed, using aerobraking it is somewhat easier in terms of deltaV than many other places), but actually landing on the planet and operating on the surface is insanely difficult. You would need a probe which has the ability to perform operations at the bottom of the ocean (due to the huge static pressure of Venus' atmosphere), while immersed in sulphuric acid at a temperature of 462 °C. – Thucydides Jan 5 at 11:02
    
Probably we will shift attention to Venus for a brief period, just enough to study the new life form, but if you are talking about colonization, Mars is far easier... – Gianluca Jan 5 at 11:12
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Only after they release an awesome movie and book, The Venusian – Wayne Werner Jan 5 at 17:12
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@WayneWerner - That movie is much shorter, and ends just a few minutes into the movie after the protagonist's anti-pressure suit is breached, and he is simultaneously crushed by Venus's 1000psi atmosphere, boiled by 800 degree F temperatures, and his body is dissolved by the sulfuric acid in the atmosphere. – Johnny Jan 6 at 4:55
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@Johnny I'd watch it. – Shane Jan 6 at 17:58
up vote 24 down vote accepted

If there are credible signs of multicellular life, and not just hard-to-explain sensor readings that might be consistent with some sort of life, the priority of Venus for further automated science missions would go up. But there would also be concern of contamination — both ways.

Mars remains the better option for the first permanent off-Earth settlement.

  • Heating is easier than cooling.
  • Near vacuum is better than 93 atmospheres pressure.
  • A lower gravity means easier crew return missions.
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All of the exploration/habitation plans I've seen for Venus explicitly avoid the surface in favor of floating cities above the cloud layer. Apparently, there's a nice zone that is about earth atmosphere in terms of pressure and temperature, and is above the sulfuric acid clouds. I haven't heard of anyone seriously considering a Venus ground colony without massive terraforming first. – Green Jan 5 at 13:56
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+1 While Mars might prove to be less likely to harbor life than Venus, it remains the best candidate for astronauts to create a colony because of what it lacks compared to the latter, specifically brutal heat due to runaway greenhouse gases in a very dense atmosphere. Our artificial habitats will work much better there because we have spent decades learning to survive in a cold vacuum, as that has been the setting for every manned mission thus far. – Prof. Bear Jan 5 at 14:00
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The nice thing about the surface of Venus (quite possibly the only nice thing about it) is that we really don't need to worry about contaminating it with Earth life. No known Earth organism, not even the hardiest hyperthermophiles, comes anywhere even close to being able to survive (much less reproduce) on the surface of Venus. – Ilmari Karonen Jan 5 at 16:29
    
Good catch on the gravity well issue. – Wingman4l7 Jan 5 at 18:22
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@IlmariKaronen right. More interesting would be the question of how conceivable it would be for life from Venus to survive in Earth-like conditions. Likely, a Venus lifeform would see Earth as a highly alkaline ice desert with laughably thin atmosphere. OTOH, it's probably much easier for an extremophile organism to contain its own Venus-acidic environment than it is for an earth extremophile to shield itself from such an environment. – leftaroundabout Jan 6 at 17:00

From a science point of view, yes, if life were discovered on Venus, there would be an immediate switch in priorities. Scientifically this would be huge. (And contrary to other answers, science rather than colonisation is the main reason for funding space missions in the current political climate.) It would be our first discovery of life anywhere away from Earth, so there would be a huge wave of media excitement and popular interest, and as a result, funding for space missions, especially Venus ones, would go up for a while.

Scientists all over the world would be intensely excited to answer all sorts of questions about Venus life: did it arise independently of Earth life, or was life transported from one planet to another via meteorite impacts, which is thought to be possible? Does Venus life use the same amino acids and nucleic acids as Earth life, or is its chemistry completely different? How does life survive in the incredibly harsh environment on Venus, and how many places on the planet can it live? There is basically nobody in biology or planetary sciences who wouldn't immediately want to know all that. Then there's all the potential medical applications of a whole other biosphere full of biologically active molecules that are probably not found on Earth. So basically it's a no-brainer: there's no doubt that if this was discovered there would be at least one follow-up mission, perhaps several, designed specifically to study it. This would indeed quite likely involve cuts in funding for Mars missions, because that's just the way things work.

These Venus missions would not be manned, due to Venus' thick corrosive atmosphere. This not only makes it extremely hard for even an unmanned spacecraft to last very long but also means that you can't blast off from Venus unless you manage to take something the size of a Saturn V with you and land it on the surface - that's currently quite some way beyond what humans are practically capable of. So these would be robotic missions with specifically designed experiments for studying Venusian biology. Perhaps people would consider a sample return mission - i.e. an unmanned spacecraft that picks up a sample and takes it back to Earth - though I would guess that would be unfeasible at our present stage of development.

However, there is a big caveat to be mentioned. Life is thought to be very unlikely on Venus, due to the extremely high temperature and sulfuric acid rain - certainly no known Earth life can survive there. We can suspend disbelief and imagine that life finds a way to survive there anyway, but it also poses another problem: no probe sent to Venus in 2022 will include equipment to detect life, because nobody expects to find it there. Detecting life in non-Earth-like soil is hard - even the recent Mars probes don't carry equipment designed to do that, because it would be prohibitively expensive to do so. So the probe will not carry PCR equipment for detecting DNA; it will not carry an experiment to culture any bacteria it might happen to find, and it will not carry the microscope and special dyes that would be needed to attempt to observe cells directly. Even if the soil on Venus were teeming with as many bacteria on Earth, it would look as lifeless as Earth dirt to the rover's sensors. If you're really lucky a growing bacterial colony might be observed by the cameras, but it would just look like a small stain that changes slowly in size, and it would be impossible to be sure that that was actually life rather than just a chemical phenomenon.

For these reasons, it's extremely unlikely that a near-future Venus rover would find life on Venus even if it were there - they only way I can think of it happening is if there is not just bacteria but actual complex multicellular life that can be directly and unmistakably observed by a camera.

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Trying to detect DNA on Venus would be pointless, anyway, since it would be destroyed by the ambient environment; if there was life down there, it would have to be based on some completely different kind of biochemistry. – Ilmari Karonen Jan 5 at 16:38
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I tend to agree. Life on Earth has surprised us in the past by surviving in places where we were sure it couldn't, but the conditions on Venus are quite a lot more extreme than anywhere life survives on Earth. – Nathaniel Jan 6 at 1:37

Let's assume that all space missions ultimately aim to colonize their target planets (Venus and Mars in this case). You should focus on using local resources in order to create a successful colony as proven by previous colonial attempts on Earth. You can't just say "I'm going to take whatever I need with me." With that in mind there are solid findings about existence of water (both in frozen and liquid forms) on Mars. Also studies show that humanity can use Mars' existing resources to produce other necessities like fuel and oxygen. These are (along with a low gravity and other pros given in previous answers) huge advantages which Venus can't provide. Theoretical microbial life on Venus can only prove one thing : life can exist in harsh environments (as we know from our own experience on Earth). But that's not enough to convince humanity to change its target.

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I'd say no for this reason

$$\begin{array}{c|c|c|} \text{Planet} & \text{Min surface temp} & \text{Max surface temp} \\ \hline \text{Mercury} & -275°\text{F} ~ (-170°\text{C}) & +840°\text{F} ~ (+450°\text{C}) \\ \hline \text{Venus} & +870°\text{F} ~ (+465°\text{C}) & +870°\text{F} ~ (+465°\text{C}) \\ \hline \text{Earth} & -129°\text{F} ~ (-89°\text{C}) & +136°\text{F} ~ (+58°\text{C}) \\ \hline \text{Moon} & -280°\text{F} ~ (-173°\text{C}) & +260°\text{F} ~ (+127°\text{C}) \\ \hline \text{Mars} & -195°\text{F} ~ (-125°\text{C}) & +70°\text{F} ~ (+20°\text{C}) \\ \hline \end{array}$$

Mars is positively comfortable compared to Venus. It's not that Venus is harder, it's the sheer hostility of the place.

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Incidentally, the coldest known place in the Solar System is at the bottom of one of the Moon's polar craters. space.com/7311-moon-craters-coldest-place-solar-system.html Lowest temperature is -397 F (-238 C / 35 K). – Jim2B Jan 5 at 16:53
    
@MichaelKjörling The table has a list of data sources linked at the bottom. Notably, all 5 links are gone. This would be my guess as to why. It also differs from a NASA source that actually exists by a couple degrees: solarsystem.nasa.gov/planets/mercury/facts. (That link can be found by following links from the article about World Book articles being taken down, so it seems to be a suitable replacement.) Maybe it would be better to just compile the data from somewhere else. – jpmc26 Jan 5 at 19:36
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I doubt the surface temperature of Venus is as stable as indicated by that table. – kasperd Jan 6 at 0:54
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@kasperd It appears that the temperature on Venus is fairly stable, but does vary based on altitude: How Hot is Venus? – Snowman Jan 6 at 1:42

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