Since Nasa's Viking Mission tested Martian soil samples back in the 1970s, we've known the surface of Mars to be a desert – inhospitable to life as we know it. But as missions to Mars focussed on what lies beneath the surface, a different picture has started to emerge.

This discovery of water beneath the planet's South Pole is the result of radar echoes that were picked up by an instrument on a spacecraft that's been orbiting Mars for 15 years. To stay liquid beneath the long-frozen surface of Mars, the researchers say this sub-glacial lake must have huge amounts of salts dissolved in it.

Its extreme cold and saltiness would make it a very harsh environment for any living thing. But the lead researcher, Professor Roberto Orosei from the Italian National Institute for Astrophysics, said the existence of organisms there, was not impossible.

To search for life in this newly discovered lake though, scientists will need to send a robot that's able to drill through the mile of ice encapsulating it.  But at least the teams looking for life on the Red Planet will now know where to start their search.