Roving on the Red Planet. (Astronomy).

Last month, NASA selected the landing sites for identical rovers scheduled to begin exploring the Martian surface next January. Both sites show evidence they once contained liquid water and might therefore harbor fossils of primitive life.

The 150-kilometerwide Gusev Crater will be examined by a rover scheduled for launch May 30 and set to parachute onto the Red Planet on Jan. 4, 2004. Located 15[degrees] south of the Martian equator, the crater has what appears to be a dry riverbed flowing into it, suggesting "there had to have been a lake [there] at some point," notes principal investigator Steven W. Squyres of Cornell University.

The other rover, set for launch June 25 and to arrive on Mars on Jan. 25, 2004, will explore Meridiani Planum, an area with deposits of an iron oxide called gray hematite. This material, coarser than the reddish hematite that gives Mars its rusty color, usually forms after hot water flows through and dissolves iron from rocks. As the water cools, the gray oxide precipitates out and collects in the cracks and veins of rock. Meridiani lies about 2[degrees] south of the equator and halfway around the planet from Gusev.

The solar-powered rovers are designed to last at least 90 Martian days. After that, dust accumulation on solar panels may diminish their power.--RC.