Dry Ice Storms on Mars?

Bombarded by violent storms of dry ice, the red planet's ice caps may have fewer silent nights than generally thought, according to new weather models.
Climate experts have long agreed that all is calm during the polar nights—the sunless winter months on Mars' north and south poles.
The poles are too cold, and the carbon dioxide rich atmosphere too thin and clear, to result in exciting weather, or so the thinking goes.
But now there's mounting evidence that temperature differences in the polar night stir up the atmosphere, creating storms..........

National Geographic News

Aquifers on Mars

Substantial quantities of liquid water must have been stably present in the early history of Mars. The findings of OMEGA, on board ESA's Mars Express, have implications on the climatic history of the planet and the question of its 'habitability' at some point in its history..........

Science Daily