'Up to half' of Mars may have ice

A new method of scanning Mars has shown that ice may be seen beyond the known ice of the planet's North Pole. The ice deposits are so immense that they would cover the planet in an ocean if they were to melt. "By comparing seasonal changes in thermal infrared patterns" through a new method connected to the Odyssey spacecraft, readings can be accurate to within hundreds of meters. This new method shows that water ice may be approximately 1/3 of the planet's surface area. The new thermal imaging also shows that the ice can vary considerably with depth.

http://news.bbc.co.uk/2/hi/science/nature/6617851.stm