Early Mars Was All Wet

New observations made by NASA's Mars Reconnaissance Orbiter (MRO), currently circling the planet, have revealed evidence that vast regions of the southern highlands of Mars were altered by water in a variety of environments billions of years ago.

Water is a key condition for life as we know it. Though there is no firm evidence that Mars has ever harbored life, knowing that the planet was once wet suggests that it was at least habitable in the past.