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Re: Venus's atmosphere



On 07/23/2003 11:07 AM, Frank Cardulla wrote:
> Why is it that Venus has been able to retain an atmosphere that
> exerts a pressure about 90x that of the atmosphere on Earth? The
> mass of Venus is less than that of Earth,
...
> Anyone have a reasonable simple explanation?

I don't think this is one of those physics-is-fun
questions that you can solve on the back of an
envelope using a handful of facts from the almanac.

Basic physics makes a clear, simple prediction,
but it may not be what you wanted: in the long
run, there will not be any atmosphere on Earth,
Venus, or anywhere like that. It's simple: a
fraction of the molecules have escape velocity.
It's a roach motel in reverse: they can check
out, but they never check back in.

So ... what we actually see today is highly
dependent on initial conditions and boundary
conditions. Volcanos and such.

The existence of liquid water affects a few
secondary questions, but not the primary question.