When the poles of Mars freeze over, what chemical makes up the frozen plains?

The poles of Mars do have frozen water, but what makes up the plains of ice that look similar to the poles on Earth is actually carbon dioxide freezing over. In the summers on Mars, the atmospheric pressure rises as it evaporates into the atmosphere, and in the winters, the atmospheric pressure lowers as the carbon dioxide freezes onto the poles.

Asked by Tori Highley · Last updated 5 years ago · 13.2K views · SOURCE