Why Mars?

Why Mars?
Why Mars? The behavior of frosts on Mars may sound like an arcane subject for study, but when you consider that those frosts are made of carbon dioxide and water, and that water is a key to life, the importance becomes clear. This is a crater near Mars' north polar cap, which, like Earth's maintains a permanent covering of frozen water. This crater also retains a permanent layer of frost, unlike other craters of similar size, shape, and location. Why some craters defrost while others don't is one of the many enigmas of Mars. Mike Malin