Did Mars have water? The ground seems to say yes. The presence of a particular type of hematite, a mineral mostly associated with water, along with large, sandy areas, indicates that the red planet once had a supply of the liquid, said Robert Denise, a scientist at NASA’s Jet Propulsion Laboratory and a member of the flight development software team for the Mars Exploration Rovers program. Denise is attending the Hot Chips conference taking place this week at Stanford University.