The European Space Agency has released an amazing photo (below) of a large lake of water ice in a crater on Vastitas Borealis in the northern hemisphere.

There is more info/news at:

• ESA – Perspective view of crater with water ice – looking east
• BBC News – Science/Nature – Ice lake found on the Red Planet
• Planetary Society – Mars Express: High Resolution Camera Returns Close-Up Images of Water Ice Near North Pole

You can also browse the ESA’s Mars Express photos, at the time of writing the ice crater were the latest ones there.

This photo is linked from the Planetary Society.