Mars rover still stuck in martian sand

PASADENA, Calif., Aug. 24 (UPI) -- NASA engineers have added another test rover to a project designed to develop a strategy for freeing Mars rover Spirit, which is stuck in loose martian sand.

The engineering team has begun using a lighter weight test rover that does not carry a science payload or robotic arm, as do Spirit and Opportunity on Mars, said scientists at the Jet Propulsion Laboratory, where the testing is being conducted. "While the primary test rover's weight on Earth is greater than Spirit's weight on Mars, the second rover is even lighter on Earth and closer to the weight of Spirit on Mars," NASA said.

Space agency engineers said comparing motions of the two test rovers in duplicated drives will aid in interpreting effects of differing gravity on rover mobility.

"There is no perfect Earth analog for Spirit's current situation," said JPL's John Callas, project manager for the twin Mars Exploration Rovers. "There's less gravity on Mars, little atmosphere, and no moisture in the soil where Spirit is. It is not anything like being stuck in sand or snow or mud on Earth. Plus, since the rover moves only about as fast as a tortoise, you cannot use momentum to help. No rocking back and forth as you might do on Earth."

Spirit has been stuck since April.