Jan. 18, 2000 -- After more than a month of searching for a signal[1] from NASA's Mars Polar Lander, mission controllers on Monday gave up hope of saving the $165 million mission to Mars. The last effort to communicate with the three-legged lander ended at 11 a.m.

"We didn't see anything," says Richard Cook, the spacecraft's project manager at NASA's Jet Propulsion Laboratory. Now, space agency scientists and engineers will focus[2] on what could have gone wrong and how to avoid the same mistakes in the next mission.

Polar Lander was supposed[3] to have touched down Dec. 3 for a 90-day mission near Mars' south pole to study the atmosphere and dig for ice. It was last heard from minutes before beginning its descent.

Instead of reveling[4] in new pictures and science, controllers have been methodically testing dozens of different scenarios to explain the silence. Investigators will continue to seek an explanation for the failure and have launched a review of the Mars program, which also lost an orbiter in September.

Another lander and orbiter are scheduled to be launched next year, but at least part of the mission is now in doubt. "The orbiter for sure will happen. There's no issue there," Cook says. "The lander they're still talking about."

Mars Polar Lander could have touched down on the side of a canyon and toppled over. Or it could have exploded before entering the atmosphere. Its radio systems might have failed. Or it could have sunk into Martian dust. Attempts to capture a picture of the lander's parachute with the orbiting Mars Global Surveyor also were unsuccessful. It's possible the reason for the mission's failure may never be known, but investigators will make recommendations for future missions.