"This weeks test is a real long-shot, and I wouldnt want to get anyone too excited about it," said Richard Cook, the Polar Lander project manager. "The signal that the Stanford team detected is definitely artificial, but there are any one of a number of places it could have originated on or near Earth. Still, we need to conduct this test to rule out the possibility that the signal could be coming from Polar Lander."

The Stanford team sent commands to the Polar Lander in December and January, telling it to send a signal to the 150-foot (45-meter) antenna in Palo Alto, California.

Engineers reported at the time they saw no signal in real time. However, subsequent processing of the data showed what could have been a signal originating from Mars during the December 18 and January 4 attempts.

Although that data took weeks to sift through, engineers expect it will take only days to scan the data expected early Thursday EST for any trace of the lander.

NASA can only assume the $165-million Mars Polar Lander alighted on Mars on December 3, since it has not been heard from since then.

Officially, NASA gave up listening for the Polar Lander on January 17. Ongoing efforts using the currently orbiting Mars Global Surveyor to image where the spacecraft might have landed have also failed to detect the craft.