Martian glaciers caused by snow
Pictures of the red planet taken in the last few years have shown ice-rich landforms near the equator that suggest glacial movements as recently as 350,000 - 4 million years ago. Scientists believe these deposits on Mars to be remnants of snow. The theory is that Mars used to have a different tilt, with the poles pointing more towards the sun. As a result, the polar ice caps melted releasing vapor, which was blown south over the Tharsis Montes and Olympus Mons volcanoes, and turned to snow as it cooled and condensed, thus forming the glaciers. The model is described in the Jan. 20 journal Science. "The findings are important because they tell us that Mars has experienced big climate changes in the past, the kinds of climate change that led to the Great Ice Age here on Earth," said Brown University’s planetary geologist James Head. "The findings are also interesting because this precipitation pattern may have left pockets of ice scattered across Mars. This is good information for NASA as officials plan future space missions, particularly with astronauts."
Snow on Mars Created Glaciers Near Equator, Space.com