NASA said it was investigating the type of research a stationary Spirit could do in the future. For example, it could study the interior of Mars, monitor the weather and continue looking at the deposits uncovered by its wheels, a task it has already been performing.

Mobility is still the first priority, NASA stated. Spirit's right-front wheel, which had stopped operating in March 2006, showed signs of life late last year by spinning slightly during one of the attempts to move the rover. The wheel however stopped later in another test and has not worked since.

In related news, NASA's Mars Odyssey orbiter will next week make a number of passes over the presumed dead Phoenix Mars Lander on the surface of the planet and listen for what the space agency called possible, though improbable, radio transmissions.

Odyssey will pass over the Phoenix landing site about 10 times this month and two longer listening tries in February and March trying to determine if the craft survived Martian winter and try to lock onto a signal and gain information about the lander's status.

Should the lander show signs of life, it should follow instructions programmed on its computer. If systems still operate, once its solar panels generate enough electricity to establish a positive energy balance, the lander would periodically try to communicate with any available Mars relay orbiters in an attempt to reestablish contact with Earth. During each try, the lander would alternately use each of its two radios and each of its two antennas, NASA stated.