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.
![Perspective view of crater with water ice - looking east (c) ESA 2005](http://www.planetary.org/news/2005/images/m-ex_water-ice_north-pole_medium_0728.png)
This photo is linked from the Planetary Society.