Our redder, older-looking sister planet has always been an object of interest to us Earthlings – from the giant face to the possibility of Martian life. But more boringly, scientists have always wondered if water, at some point, existed on Mars. There has been a lot of speculation that it had once existed on the red planet, but we have never really known for sure. Until now!
Apparently, more than 3 billion years ago, in the most Northern parts of Mars, an ocean took up more than one third of the surface. With research into ancient river valley networks and deltas, scientists have suggested that early Mars could have had a global water cycle much like our current hydrological configuration – proving that Earth is the younger sister and not yet all dried up. But where did all the water go? Hopefully future missions to the 4th rock from the sun will tell.
More info here.