In a cramped office near the University of Colorado football stadium, graduate student Shannon Pelkey is helping NASA decide where to send a pair of unmanned Mars rovers worth about $400 million apiece. Gaudy splashes of red, green and blue flash across Pelkey’s computer screen as she clicks through images of candidate landing sites for the upcoming Mars Exploration Rover mission. As a member of the tightknit community of U.S. scientists and engineers evaluating the landing zones, Pelkey is among the first on the planet to view new Mars infrared images being sent back by NASA’s Denver-built Odyssey spacecraft.