Mars Rover Maneuvers For Rim Shot

The NASA rover Spirit was ready Wednesday to make its final push to the rim of a big crater that scientists hope will provide a window into Mars' geologic history.

Spirit was close enough to snap a panorama showing the rim on the opposite side of the crater, according to the Jet Propulsion Laboratory. Spirit was expected to finish its drive and be in position to peer inside the crater with a camera on Thursday.

"We're all waiting very anxiously to see what's inside this crater," said George Chen, the Spirit flight director.

Spirit and its twin, Opportunity, have found signs of past water activity in rocks on the surface at their landing sites. The big crater is an impact crater and may provide Spirit a trove of rocks churned up from well below the surface, perhaps representing different periods in the planet's history.

Halfway around the planet, Opportunity continued to work within the tiny crater where it landed in late January.

The lead scientist monitoring the rovers' rock abrasion tools on Wednesday said that cold caused the motor on Opportunity's grinder to stall this week when it was trying to bore into a target. Stephen Gorevan said stickiness of the mechanism due to cold can be overcome by increasing voltage.

Initial explanations for the stall included dust and dirt on the tool as well as temperature variations. The tools allow the rovers to examine the interior of rocks with microscopic photography and instruments that determine composition.