When Chris Leger drives on the job, his vehicle moves on another planet. Leger is one of a team of scientists who develop commands for the movements of the Mars Exploration Rovers.

The rovers, Spirit and Opportunity, landed on Mars in January 2004 in search of evidence that the dusty planet once had liquid water -- a building block of life. (Scientists have long known that ice exists at its poles.)

A few months after landing and inspecting soil and rocks, the rovers found proof that water covered large portions of the red planet millions of years ago.

Leger drives the rovers by sending commands from Earth. An avid rock climber, Leger says his experiences in climbing and mountaineering come into play when plotting the rovers' moves.

"If you can sit back and look and visualize the sequence of movements you're going to use to traverse a certain section of rock, then you'll be able to climb it much better," he says.

Leger grew up in southern Maryland and went to Carnegie Mellon University in Pittsburgh, where he received a bachelor's degree in electrical and computer engineering. He also earned a master's degree and doctorate in robotics.

"I guess always as a kid I've been interested in how the world works and exploration," he says. "I remember reading books about Viking and Voyager and all the other missions that explored the solar system when I was a kid and at some point I decided that's what I wanted to do."

Leger adds that he hopes humans get to Mars within his lifetime. "Technologically it's very feasible. ... I think it's going to be more a matter of whether the people of America and of the world decide it's something worth doing and want to commit the resources and time to it."

-- By Larisa Epatko, Online NewsHour