Researchers discover lake beneath southern pole of Mars. 

A group of researchers have discovered a lake beneath the southern pole of Mars, according to a paper published today in the journal Science.

This new finding comes from research using the Mars Express spacecraft that has been orbiting the red planet since December 25, 2003.

One of the suites of instruments carried by Mars Express is MARSIS (the Mars Advanced Radar for Subsurface and Ionosphere Sounding), which allows researchers to use radar to study features beneath the planet’s surface.

Using observations spanning a period of four years, a team of researchers from Italy found evidence of a large lake of salty water, buried 1.5 kilometres beneath Mars’ southern polar cap. That lake is at least 20 kilometres across and seems to be a permanent feature.

The reason people are excited about this discovery is because on Earth, everywhere you find liquid water, you find life. NASA has long espoused a philosophy of “follow the water” in its program of astrobiological research – trying to answer the question “are we alone?”