Mars spacecraft gets a landing site.

It doesn't look like much, just a strip of gentle, rolling plains. And that's precisely the point. The region on the Red Planet that NASA has chosen as the landing site for the Mars Polar Lander, expected to touch down on Dec. 3, has slopes no steeper than 10 degrees. Most of it is considerably flatter.

"We chose a location with some surface features but no cliffs or jagged peaks" so that the spacecraft can land safely yet still accomplish its research goals, says project scientist Richard W. Zurek of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Unlike Mars Pathfinder, which landed on a hillier region in 1997, the lander won't have airbags to cushion its touchdown.

The smooth region lies near the northern edge of the Mars south pole's layered terrain. NASA announced its decision Aug. 25 at a press briefing in Washington, D.C.

The mission will study the layers of dust and ice that cover the pole. Changes in the thickness of these layers may indicate variations in climate over the past hundreds of thousands of years. The lander will also look for soil particles that could have formed in ancient Martian seas and later blew into the polar areas.

Ultrasharp images and laser altimeter measurements gathered by the Mars Global Surveyor spacecraft, which continues to orbit the Red Planet, were key to selecting a site. Launched in January, the lander will arrive at the end of Martian spring, a time when the sun never sets. The continuous sunshine will power the craft for 90 days. The beginning of Martian fall, when the sun dips below the horizon, will signal the end of the mission.