A prototype of two remote-controlled Mars rovers due for launch in 2003 has passed its final field tests in the desert in northern Arizona. NASA’s Field Integrated Design and Operations (FIDO) robot is a smaller, stripped-down model of the Mars Exploration Rovers – two identical robots that will explore the surface of Mars after touching down in January 2004. The rovers will have much greater mobility than the 1997 Pathfinder, and travel as far in one Martian day as the Pathfinder did in its lifetime.