Closing In on Mars

The launchpads have long since cooled following the lift-off of NASA's two Mars rovers in June and July. But the spacecraft have been pressing ahead. During a summer that Americans spent lazing or working or planning vacations, the twin vehicles, dubbed Spirit and Opportunity, have traveled 137 million miles and 91 million miles, respectively (with 166 million and 192 million more to go), on their way to touchdowns on nearly opposite sides of the Red Planet on Jan. 4 and Jan. 25.

True, you have seen a Mars landing before. Pathfinder's spectacular little rover, Sojourner--a remote-controlled vehicle about the size of a microwave oven--toddled across the Martian terrain in the summer of 1997. But you won't want to miss the show the two new ones promise to put on.

Unlike little Sojourner, Spirit and Opportunity are full-blown Mars cars, about the size of golf carts and fairly stuffed with instruments--including a bristle of cameras atop an almost 5-ft. antenna mast that will provide an eye-level view of the terrain, as opposed to the shin-level view Pathfinder provided. Like their predecessor, they will be visiting areas of the planet that scientists believe were once deluged with water, precisely the kind of spots extraterrestrial organisms would, at least in theory, love. If Mars ever harbored life, the 90 or more days Spirit and Opportunity will spend prospecting in these spots may turn up the geological evidence.

The prospect of the landings could not have come at a better time. NASA was smacked around soundly last week when the long-awaited report on the loss of the space shuttle Columbia was released. Investigators blamed the tragedy, at least in part, on the agency's lack of a crisply defined focus--particularly its largely aimless program of human exploration. But launching interplanetary probes is something NASA has always done well. At the moment, Mars is making itself a decidedly tempting target, and humanity is taking advantage of it.

The planet last week passed closer to Earth than it has in almost 60,000 years. Even as Spirit and Opportunity speed toward their wintertime rendezvous, the European Space Agency has a probe of its own on the way, a stationary lander expected to touch down on Mars on Christmas Day. The Japanese, back in 1998, launched an orbiter, which, after a circuitous route through the solar system, should arrive sometime in December.

Nonetheless, it is Spirit and Opportunity that are generating the most buzz, at least partly because the 6.3 billion of us left behind on Earth will be able to share the trip. As with the Pathfinder mission, NASA will fling open a trio of websites that will track the surface explorations as they unfold. Whatever the spacecraft learn, we'll learn along with them--and it could turn out to be plenty. "We have on these rovers so many capabilities that have never been present on another planet," says Steve Squyres, the missions' principal investigator. "I guarantee you, we're going to find new things."