I had a question or you science-y types. I've read several articles about the possibility that Mars had liquid surface water in its past. My question is with Mars being so much further from the Sun than Earth (receiving less heat from the Sun) how could it still have liquid surface water?
I know you asked this a long time ago. But, since no one actually answered, I'll post a couple of things.
Earth is actually on the warmer side of what is thought to be the "goldilocks zone", i.e. the distance from the Sun that can support liquid water. And that makes sense. The poles stay frozen most of the time on Earth, but the equator is basically never frozen. But a planet could be three times further from the Sun and still have some part of its surface warm enough for liquid water some of the time. Moreover, factors like greenhouse effect, tidal heating, vulcanism, and radioactive decay could warm the planet in ways that are hard to predict.
Wouldn't that require a much higher atmospheric pressure? :idunno:
Yes. At current pressures, water would transition directly between solid and vapor. However, the pressure was likely much higher in the past, before the solar wind stripped most of the atmosphere.
http://www1.lsbu.ac.uk/water/water_phase_diagram.html
