The proposals are due April 1 of this year, and the Langley Research Center in partnership with the Jet Propulsion Laboratory and with Lockheed Martin, with the Draper Lab and Aurora Flight Sciences, is proposing a robotic airplane to fly over the surface of Mars, about a mile above the surface.

NPR: Revisiting the Viking Missions to Mars

"Oil is out of sight when it's below the surface, but it's not out of mind, " said Edward Overton, an emeritus professor of environmental sciences at Louisiana State University.

WSJ: Gauging Harm to Ecosystem Could Take Years