John M. Grunsfeld, Associate Administrator for the Science Mission Directorate at NASA, speaks at a press conference announcing that NASA has confirmed that liquid water flows on the surface of Mars, at NASA headquarters in Washington, D.C. on September 28, 2015. NASA's Mars Reconnaissance Orbiter (MRO) provided the strongest evidence yet that liquid water flows intermittently on present-day Mars which opens up the idea that life of some kind may exist now or in the past on Mars. Photo by Kevin Dietsch/UPI