A new detailed map of Mars shows what was likely a vast ocean in the north and valleys around the equator, suggesting that the planet once had a humid, rainy climate, according to research published Monday. -- The computer-generated map, based on topographic data from NASA satellites, also shows that the network of valleys on the red planet is at least twice as extensive as previously estimated. "The relatively high values over extended regions indicate the valleys originated by means of precipitation-fed runoff erosion -- the same process that is responsible for formation of the bulk of valleys on our planet," said Wei Luo, geography professor at Northern Illinois University who co-authored the report.