Scientists think they can now tie dark streaks seen on the surface of Mars to periodic flows of liquid water.
Data from a Nasa satellite shows the features, which appear on slopes, to be associated with salt deposits.
Crucially, such salts could alter the freezing and vaporisation points of water in Mars’s sparse air, keeping it in a fluid state long enough to move.
Michael Meyer, the lead scientist on Nasa’s Mars exploration programme, and Dr Jim Green, Nasa’s planetary science director, made the announcement.
“Under certain circumstances, liquid water has been found on Mars,” Dr Green said.