[Animats]

All you need are moments when the water is liquid.

But you don't get those at such low atmospheric pressure. Mars atmospheric pressure is around 600pa. Below 611pa, the boiling point of water drops to the freezing point; you can have ice or steam, but not liquid water.

[stcredzero]

But you don't get those at such low atmospheric pressure. Mars atmospheric pressure is around 600pa.

A mental exercise: Any place on Mars with higher than 600pa pressure?

[qbrass]

https://en.wikipedia.org/wiki/Hellas_Planitia

[stcredzero]

How about underground? How about the bottom of a glacier? No need to be "surfacist." ;)

[qbrass]

An unsealed hole underground would have to be dug to the same depths as that crater. If you're pressurizing it, you'll probably target 1 bar to live in it, instead of 600 KPa.

A glacier that has the pressure to melt ice, would have more than enough pressure to keep it from sublimating. A rough estimate says that a foot or so of ice could provide over 600KPa of pressure, but that doesn't account for any means of keeping the water liquid or the ice solid. However, I wouldn't expect to actually find that on Mars. You might be able to keep water that way for a while until it froze again.

[hermitdev]

They do have recent satellite images that appear to show signs of water running down ravines at certain times of the Mara year. Don't have a citation handy, though.

[smcnally]

That explanation is sublime.