Frosty Mountains on Mars . ... Credit Copyright: MSSS , JPL , NASA Explanation: What causes the unusual white color on some Martian mountains? The answer can be guessed by noticing that the bright areas disappear as springtime takes hold in the south of Mars: dry ice. Unlike water ice, dry carbon dioxide ice sublimates directly to gas from its frozen state. The frosty mountains, named Charitum Montes , have been covered with carbon dioxide ice over the Martian winter. ...