So long, Surveyor.

After 8 years of relaying pictures, topographic maps, magnetic field data, and compositional information from above the Red Planet, NASA's Mars Global Surveyor spacecraft appears to have called it quits.

The satellite hasn't been heard from since Nov. 2. Scientists speculate that a solar panel on Surveyor can no longer pivot properly. This malfunction would prevent the craft from generating enough power to communicate. A search by NASA's most recent emigre to the planet, the Mars Reconnaissance Orbiter, couldn't locate Surveyor, says Mars program manager Fuk Li of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Surveyor arrived at Mars in September 1997 and began its main mapping mission 2 years later. It sent more than 240,000 images to Earth, including pictures of gullies that appear to have been recently carved by liquid water. Surveyor scientist Michael C. Malin of Malin Space Science Systems in San Diego and his colleagues report the latest evidence of recent water in the Dec. 8 Science.

Surveyor pioneered the routine use of aerobraking, a practice that entails repeatedly dipping into the Martian atmosphere to reshape its orbit from a highly elliptical path into a nearly circular one. The mission had been designed to last only 2 Earth years but endured the longest of any spacecraft sent to Mars. Surveyor withstood such challenges as a broken wing, worn-out parts, and a failed gyroscope.--R.C.