Nasa scientists discover evidence of water on Mars

Nasa scientists have today revealed there is evidence of water on Mars in a major announcement expected to raise hopes of discovering life on the planet.

Researchers said there was now proof that liquid water runs down canyons and craters in the summer months leaving dark stains on the Martian terrain before they dry up in the autumn.

Images taken from the Mars orbit show long, narrow streaks caused by summertime flows on cliffs and valleys, yet scientists said they remain unsure where the water has come from.

One theory put forward is that liquid rises up from underground ice or alternatively that it is condensed out of the thin atmosphere.

Michael Meyer, lead scientist on Nasa's Mars exploration programme, said: "There is liquid water today on the surface of Mars.

"Because of this, we suspect that it is at least possible to have a habitable environment today.”