On some parts of Mars, it gets cold enough for a gas to freeze out of the atmosphere that does not freeze out by itself at the temperatures and pressures on Earth. This gas makes up some of the polar caps on Mars and is:

Question

Quizplus · Accepted Answer

The gas that freezes out of the atmosphere on Mars is carbon dioxide, which makes up some of the polar caps on the planet. Water ice and traces of other gases such as argon and methane have also been detected on Mars, but they do not freeze out at the temperatures and pressures seen on Mars as much as carbon dioxide does.

On Some Parts of Mars, It Gets Cold Enough for a Gas