First evidence of planet-wide groundwater system on Mars

Mars Express has revealed the first geological evidence of a system of ancient interconnected lakes that once lay deep beneath the Red Planet’s surface, five of which may contain minerals crucial to life. Mars appears to be an arid world, but its surface shows compelling signs that large amounts of water once existed across the planet.
Read more: http://www.esa.int/Our_Activities/Space_Science/Mars_Express/First_evidence_of_planet-wide_groundwater_system_on_Mars?source=Snapzu