# What air pressure is needed on mars, to have fluid water?

The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi), about 0.6% of Earth's mean sea level pressure.

There is a lot of frozen ice on mars, but it can't melt, because of the low air pressure, it sublimates to steam if it's warm enough. But what air pressure is needed, to have 4°C fluid water on it's surface?

• Thiss smells like homework. Have you tried looking at a phase diagram for water?
– Sean
Commented Jan 6, 2015 at 14:21
• This isn't homework. I watched a documentary about Mars, and I'm curious, if it could have oceans, or not Commented Jan 6, 2015 at 14:26
• What @Sean means is that it is similar to a homework-like exercise. You are essentially asking us to do the math for you; to solve a problem for you. When what you should be asking is how such a problem could be solved by you; what the tools are to figure this out and what the physics behind them are
– Jim
Commented Jan 6, 2015 at 14:30
• Sorry for that type of question. I haven't heard about triple point yet, so that is, what I was looking for. And now I can do the math, or look at the diagram Commented Jan 6, 2015 at 14:42