The ESA orbiter Mars Express found traces of Water on Mars
http://www.esa.int/export/SPECIALS/Mars_Express/SEM8ZB474OD_0.html

OMEGA observed the southern polar cap of Mars on 18 January 2004, as seen on all three bands. The right one represents the visible image, the middle one the CO2 (carbon dioxide) ice and the left one the H2O (water) ice.

The blue thing is not water, but a channel (Reull Vallis) once formed by flowing water.
This is too cool !