Steve Squyres, principal scientist of NASA's Mars Exploration Rover program, poses next to a full scale copy, minus some instruments, of Spirit and Opportunity, two identical robot explorers currently enroute to Mars, at a mockup of the Martian surface in a parking lot behind the Jet Propulsion Laboratory in Pasadena, Calif., Nov. 21, 2003. The NASA rover program is just one of several missions that in the next few weeks will try to provide answers to questions scientists have aboutthe Red Planet. (AP Photo/Reed Saxon)