The traffic on Mars is expected to double in the near future. NASA plans to launch two large scientific rovers to the red planet in 2003, rather than the original plan for just one, said Dr. Ed Weiler, Associate Administrator for Space Science, NASA Headquarters, Washington, D.C.

Both Mars rovers, to be built, managed and operated by NASA's Jet Propulsion Laboratory, Pasadena, Calif., currently are planned for launch from Cape Canaveral Air Force Station, Fla. The first mission is targeted for May 22, with the second launch slated for June 4. After a seven-and-a- half month cruise, the first rover should enter Mars' atmosphere January 2, 2004, with the second rover bouncing to a stop on the Martian surface January 20.

The rovers will be exact duplicates, but that's where the similarities end. Relatives of the highly successful 1997 Sojourner rover, these 150-kilogram (300-pound) mobile laboratories may look and act alike, but they're going to decidedly different locations.

"For the first time, science and technology have given us the capability to explore alien planets in ways that used to exist only in science fiction movies," said Weiler. "To have two rovers driving over dramatically different regions of Mars at the same time, to be able to drive over and see what's on the other side of the hill -- it's an incredibly exciting idea." Weiler added, "I think everyone on Earth who has ever dreamed of being an explorer on an alien planet will want to go along for the ride as we explore the surface of Mars."