With the success of twin rovers on the Red Planet, Steven W. Squyres and his team are showing how to conduct robotic missions–and setting the stage for human exploration. A professor of astronomy at Cornell University, Squyres, 48, is the principal investigator for the Mars Exploration Team, which consists of 170 members. He is responsible for all the scientific activities of both the Opportunity and Spirit rovers, leading colleague John Grotzinger to liken him to a “flea on a hot griddle,” with his hands in everything.