Everyone has known for quite a long time that solid water – ice – forms on the Martian poles.
But now, what scientists have confirmed is the existence of liquid, actually flowing on the surface of the planet. In 2011, NASA first noticed dark lines on the surface, appearing most prominently during the Martian summer.
NASA immediately suspected that these lines may represent liquid water, darkening and dampening the Martian surface. New imaging technology provided the strongest evidence that these lines may represent liquid water.