Rolling along. Two rovers will explore the martian surface in 2004.

Double Feature on Mars

Two failed missions in the past year triggered a scathing report about NASA's entire Mars program and led the agency to rethink future missions (ScienceNOW, 29 March). Today's announcement marks a renewed commitment to explore the planet. By sending two rovers, the agency hopes to hike its chances of success. Doubling up makes the mission more expensive--total cost is now estimated at $600 million--but not twice as expensive as sending just one craft, says NASA's space science chief Ed Weiler.

The rovers will have the same landing mechanism--a parachute and a cushion of air bags to break their fall--as the famous Mars Pathfinder mission, which captured the world's attention in 1997. But the new rovers will have greatly extended capabilities, says Cornell University researcher Steven Squyres, the principal investigator for the mission's science program. They are designed to travel 100 meters a day--about the total mileage of Pathfinder's rover. They will also carry a rack of new instruments, including a microscope and imager to study rocks up close, a device for grinding away the outer layers of rocks, and several spectrometers. Field tests in Nevada and the Mojave Desert have been successful, Squyres says.

NASA scientists have yet to decide on the exact landing sites, but Mars program scientist Jim Garvin says areas that might have contained large bodies of standing water--such as a crater called Holden--are strong candidates. "There's certainly no lack of good places to land," Squyres says.

Related sites

NASA Mars Exploration Program

Athena Mission to Mars