As I understand it Venus’ extreme atmosphere is due to a runaway greenhouse effect. Could this have been caused by a civilisation’s industrial processes?
Bonus question: if we really wanted to, could we copy Venus’ atmosphere by releasing all our planet’s greenhouse gasses?
It would take a very advanced, very silly civilization to boil an entire planet’s worth of water when any such civilization would (hopefully) be able to understand stars enough to know that having a tiny planet near a hot star without any sort of carbon cycle was going to have runaway greenhouse effects sooner or later anyway, with or without their help.
As for whether we can do it on Earth, the IPCC says no, but apparently some people think it’s possible to get bad enough to disturb life even if the oceans aren’t boiled away:
Sounds like an Edgar Rice Burroughs story. 
I would think that the greenhouse effect would kill everyone off before things got that bad.
OP: +1 for username / topic combination.
If someone from an ancient alien civilization came to boil away the oceans on Venus (or Earth), a Fiendish Astronaut would be just the one to do it! 
Could have been caused by anything. I have not heard of any evidence at all that suggest a pollution-producing civilization was responsible.
Has anyone looked for any evidence? And what signs of an ancient civilization could survive in the hell that is Venus?
I believe that Fiendish Astronaut is suggesting that the ancient civilisation lived on Venus when it was still Earth-like; in fact Venus may never have been very Earth-like, even in the period when it had water. The slow rotation suggests that the planet has always been uninhabitable, for any kind of life we are familiar with.
Very little. Not only are the present conditions hellish, but instead of Earth-style plate tectonics Venus apparently undergoes a “global resurfacing event” every few hundred million years or so where the surface is essentially turned over and reformed.
Indeed, it is just a fanciful but dark theory. Obviously I don’t think it is likely and even if it was, any evidence for civilisation would have melted away long ago. The slow rotation point is interesting - perhaps the answer then is no.
Kardashians?
Another weird thing about Venus is that its impact craters only go back so far in age. This, combined with the planet’s lack of plate tectonics, has led to the theory that Venus lacks a good mechanism to shed heat from its interior, and what happens over time is that the planet just gets hotter and hotter until the surface melts. Then all of the heat is released, the surface cools and solidifies, and the process starts all over again.
I don’t know how universally accepted this theory is, but it does explain why the surface of Venus only appears to be about 500 million years old when the planet itself is much older than that.
It took life on earth about 3.5 billion years to go from nothing to us semi-intelligent apes. If life just generally takes that long on average to create an intelligent species, then it is difficult to imagine life evolving that far in such a cycling, overheating environment.
Of course the ancient aliens folks can always come up with some weird alien explanation that explains the destruction of the entire surface of Venus.
I’ve wondered if there was an era in its early history when Venus might have been habitable,
Robert Heinlein thought so.
Consider: Venus’ atmosphere is about a hundred times thicker than the Earth’s, and carbon dioxide is mostly oxygen. So even if we used up all of the oxygen in our atmosphere burning it with carbon, we still wouldn’t have anywhere near as much carbon dioxide as Venus.
You must not hang out much in the AGW threads on this board.
Look for space probes they sent out into solar orbit?
If it goes through such a 500 million year cycle would it not seem to follow that it’s possible at some stage in that 500 million year cycle it becomes habitable if only for a short period. (If we can call a few million years a short period)
Is it possible that the hellish atmosphere is the reason for Venus’ lack of plate tectonics? That is, the high temperature of the atmosphere might change delta-T across the crust enough to prevent is from breaking into plates. So if Venus once had an Earth-like atmosphere it might have had Earth-like plate tectonics, and no global resurfacing.
Where did all that carbon dioxide come from?
