PASADENA, Calif. -- NASA's Spirit rover completed a series of three turns atop its lander Wednesday, putting it in position to roll onto the surface of Mars and begin its explorations, mission members said.
The rover was expected to move about 10 feet off the lander and onto the surface early Thursday, the 12th day of its mission.
The six-wheeled robot, which had been mostly immobile since landing Jan. 3, rolled about 10 inches on its platform Tuesday.
On Wednesday, it completed the last of three turns that rotated it 115 degrees. It also had finished photographing its surroundings.
"Really there is nothing left to do on the lander for Spirit, so tomorrow we are going to egress onto the surface of Mars," mission manager Jennifer Trosper said.
Once Spirit is on the ground, it will take a parting photo of the inert lander with its rear cameras.
"We really want to see that," said Kevin Burke, a mechanical engineer overseeing the roll-off process.
The rover will first explore a crater and may then try to reach distant hills, a course roughly plotted out after National Aeronautics and Space Administration pinpointed Spirit's location on Mars.
"We know where we are now and we also know where we're going," Steven Squyres, the mission's main scientist, said at a news conference Tuesday at NASA's Jet Propulsion Laboratory.
Spirit is expected to follow a meandering path, pausing to sample rocks and soil in its search for evidence of the past presence of water on the dusty surface of Mars. One such target could be "Sleepy Hollow," a shallow nearby depression that intrigues scientists.
Spirit's first major destination is an unnamed crater an estimated 825 feet away. The asteroid or meteor that punched out the crater could have exposed ancient rocks that may reveal to Spirit and its half-dozen instruments the evidence that the robot was sent to find, Squyres said.
After that, NASA may send Spirit toward a cluster of hills to the southeast. But the hills are nearly two miles away, or about five times farther than Spirit is expected to be able to travel.
Before rolling for the first time, the rover cut the last cable attaching it to its lander and began a three-part turn to line it up with the exit ramp it should use to reach the ground, flight director Chris Lewicki said Tuesday.
Once it reaches the crater, Spirit should be able to examine the rocks that ring the depression. If the rover manages to climb the 18-foot-high lip of the crater, it should be able to catch a glimpse of dunes that scientists believe fill the bowl.
Spirit would then strike out to its southeast, toward a set of tawny hills an estimated 330 feet high.
Scientists believe the 95-mile-diameter depression in which the rover landed once contained a lake. If so, the hills could preserve evidence of waves that lapped against their slopes, Parker said. Even if Spirit fails to reach the hills, its camera's 20/20 vision should be able to pick out the horizontal markings that would suggest that evidence, Parker added.
Spirit probably will conk out before reaching the hills, however. Martian temperatures of 100 degrees below zero Fahrenheit and colder wreak havoc with spacecraft electronics and other components, stressing and eventually breaking them. The last rover NASA sent to Mars, 1997's Sojourner, lasted nearly 90 days before it succumbed to the cold.
The $820 million Mars Exploration Rover project includes a second, identical rover named Opportunity that is expected to land on the opposite side of the planet on Jan. 24.
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