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I define "Venusian world" to be high pressure, thick atmosphere, and high temperatures. Assume the atmosphere is similar to Venus, but whatever gets the same effect and supports life is fine.

I'm envisioning a six-limbed sentient species that's nearly blind and uses sonar to "see", and a primarily fungal-like plant life, with possibly some air-based floating life on the top surface, though small and non-sentient.

Would it be possible to have (water) oceans in this sort of planet and would it be possible to have water/carbon-based life forms?

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    $\begingroup$ I like the new question, too. Can we assume a similar atmospheric composition to Venus, or no? $\endgroup$ – HDE 226868 Jan 27 '15 at 15:34
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    $\begingroup$ Hmm...similar, but it doesn't have to be exact. If life doesn't work with similar, then dissimilar is fine too. $\endgroup$ – user6383 Jan 27 '15 at 15:42
  • $\begingroup$ Boiling points of water change with pressure changes...at 92 ATM (94232.25 Millibar) water boils around 495K (about 223 degrees celcius). Venus runs at about 465 degrees Celcius...if you were to reduce the heat on Venus by 265 degrees or so, liquid surface water is actually a potential. I'd imagine a much younger version of Venus may have had closer to these conditions (perhaps an older/cooler one, but Venus possesses such a strong Greenhouse effect that an older Venus may be warmer) $\endgroup$ – Twelfth Jan 27 '15 at 18:55
  • $\begingroup$ How about similar in pressure, but much cooler? Say the planet is located about Mars' distance from a sunlike star? Because I don't think you are going to get anything remotely resembling Earth-like carbon chemistry working at Venusian temperatures. Though somewhat higher temperature & pressure works - see the extremophiles living around deep ocean vents - as long as you can get liquid water. $\endgroup$ – jamesqf Jan 27 '15 at 18:56
  • $\begingroup$ Seems like @jamesqf had the same idea I had. A planetary scale event that relocated Venus to a much further orbit would work for this. Gravity only, no impact or anything...brown dwarf got too close and relocated it maybe? $\endgroup$ – Twelfth Jan 27 '15 at 19:09
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Here's some information about Venus:

  • Surface gravity: $8.87 \text{ m/s}^2$
  • Surface temperature: $737 \text{ K}$
  • Surface pressure: $\approx$ $92 \text{ atm}$

So no liquid water on the surface.

Wikipedia also mentions later on that you have to get 50,000 meters in the air before conditions become something like Earth (i.e. temperature and pressure are somewhat survivable). That gives us a nice little loophole. A little searching on Wikipedia showed that someone else had had the same idea I had: floating colonies:

(Artist's rendering of a floating habitat)

Floating habitat

Now we're getting somewhere.

Once more, I go back to my pufferpolyp, a floating creature that has an air sac carrying lifting gases. It floats along on its merry way, essentially staying at the same altitude for all its life (although when it dies, there's a chance its air sac will deflate and it will fall 50,000 meters to the surface, where it will be crushed and roasted).

Anyway, my life of choice is this pufferpolyp. Unfortunately, the amount of oxygen in the Venusian atmosphere is next to nil. Instead, there's plenty of $\text{CO}_2$. That gives us a little loophole. 50,000 feet should bring you above the clouds of sulfur dioxide, meaning that you might get some sunlight. So this pufferpolyp can use photosynthesis!

After a long time, if enough pufferpolyps are around, the upper atmosphere will turn to a less hellish mixture and could become an atmosphere of oxygen and nitrogen. Will the pufferpolyps die? Maybe; maybe not. $\text{CO}_2$-breathing life on Earth survived the Great Oxygenation Event 2.3 billion years ago. I think they'll survive. Bacteria might be able to take in oxygen and put out $\text{CO}_2$.

And if the pufferpolyps have been "deployed" by another race intent on aerial colonization . . . there's going to be a lot of changes happening soon.


There's no way that something as weird as a pufferpolyp could develop in such a hellish place. Most living things aren't born floating 50,000 meters in the air, and this is no exception. The things couldn't have floated up from the surface because they'd be squished in about 10 minutes down there. So my cop-out is that they've been put there by a race (humans?) intent on terraforming the planet, starting with the upper atmosphere.

That's not to say that it's impossible for things to live and evolve in the sky. Bacteria have been found living in our atmosphere; it's somewhat plausible that a similar thing happened on this planet, but the bacteria began evolving into multicellular organisms, eventually leading to the pufferpolyps.

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    $\begingroup$ @cntrational Under higher pressure, yes. $\endgroup$ – HDE 226868 Jan 27 '15 at 16:02
  • $\begingroup$ Sorry, accidentally deleted my comment. It was about higher pressures (98 atm) allowing water to form. $\endgroup$ – user6383 Jan 27 '15 at 16:04
  • $\begingroup$ @cntrational Yes; see, for example, this: www1.lsbu.ac.uk/water/water_phase_diagram.html#intr. $\endgroup$ – HDE 226868 Jan 27 '15 at 16:04
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    $\begingroup$ The issue with something like a pufferpolyp is that you run into an evolutionary problem. You'd basically have to figure out a way for life to evolve almost entirely in the atmosphere, which, given the resource constraints and lack of solvents, is highly unlikely. $\endgroup$ – Nick2253 Jan 27 '15 at 16:08
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    $\begingroup$ Alternatively, maybe the planet wasn't always Venusian. Perhaps it was originally more earthlike, life developed (including an ancestor of your pokemon), and then later it went into runaway greenhouse effects which caused the current atmosphere. But a few flying creatures and bacteria managed to survive and continue to evolve. Could have happened hundreds of millions of years ago to give the new atmosphere time to develop. $\endgroup$ – Dan Smolinske Jan 27 '15 at 18:15

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