Farewell to Pathfinder.

Built on a shoestring, the Pathfinder lander and its little rover Sojourner have captivated millions of people since the two landed on Mars on July 4. Alas, the arrival of autumn appears to have permanently chilled Earth's love affair with the probes.

Pathfinder has failed to transmit data from the rover or from its own cameras and detectors since Sept. 27. Ground stations have not heard even routine signals from it since Oct. 6. After a month of daily efforts to make contact, NASA decided to call it quits on Nov. 4.

"We concede that the likelihood of hearing from the spacecraft again diminishes with each day," says Pathfinder project manager Brian Muirhead of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Both the rover and the lander far exceeded their design lifetimes, but researchers had hoped the mission would last for many more months.

Flight operators believe that Pathfinder's batteries died after the Sept. 27 transmission. Without power to keep it warm, the lander was exposed to the frigid temperatures of early autumn on Mars and stopped functioning, researchers surmise.

Still, scientists will continue trying to contact the lander a few times each month. The best chances of getting a return signal may not come for another year, the next time that the warmer temperatures of summer will prevail at the landing site. For now, Sojourner, programmed to return to the lander if it stops receiving commands from Pathfinder, may be heading home toward its mother ship.