How Mars could have been warm and wet enough to form ancient valleys

http://www.dnaindia.com/scitech/report-how-mars-could-have-been-warm-and-wet-enough-to-form-ancient-valleys-1924550

The researchers said that the presence of molecular hydrogen, in addition to carbon dioxide and water, could have created a greenhouse effect on Mars 3.8 billion years ago that pushed temperatures high enough to allow for liquid water.