Twelve days after it bounced to a landing on the barren plain of Gusev Crater, NASA's Spirit rover has rolled off its lander onto the red Martian soil to begin its search for signs of water -- and life -- on the now-frozen planet.

	Ric Francis, pool photo via AP Steve Squyres, right, principal investigator for Mars Exploration Rover, and Mark Boyles, assurance manager, celebrate yesterday at NASA's Jet Propulsion Laboratory in Pasadena after receiving confirmation that the maneuver to get the Spirit rover off its lander was a success. Click photo for larger image.

Cheers erupted and champagne flowed in Mission Control at the Jet Propulsion Laboratory in Pasadena, Calif., when engineers received word about 5 a.m. EST yesterday that the roll-off was a success, setting the stage for the most sophisticated geological exploration ever of Mars.

"We have six wheels in the dirt. Mars is now our sandbox, and we are ready to play and learn," said JPL Director Charles Elachi.

The team had sent the command to leave the lander at 3:21 a.m., then waited for more than an hour and a half before learning the results.

It took the craft only 78 seconds to travel the 10 feet from the lander onto the surface, but the craft then had to locate the sun, take pictures of its surroundings and wait for a passing Mars orbiter before it could phone home with confirmation of its success.

"This is the most significant milestone in the history of the project," said principal investigator Steven Squyres of Cornell University.

Virtually all of the high-risk maneuvers of the craft are now complete, leaving geologists free to begin concentrating on exploration.

	NASA via AP This image from the Mars Exploration Rover Spirit's front hazard identification camera shows the rover's view of the Martian landscape from its new position 1 meter (3 feet) northwest of the lander. Click photo for larger image.

The roll-off had originally been scheduled for Monday but was delayed because a collapsed airbag from the Jan. 3 landing was partially blocking the planned exit ramp. To avoid the bag, engineers executed a 120-degree pivot of the rover on the lander, so it could use a different ramp.

Spirit took one last look back at the lander, transmitting home a picture of the now-empty and useless platform.

Engineers spent the rest of the mission day purging now-useless software from the rover and performing other housekeeping tasks to prepare for Spirit's 90-day traverse of the Martian surface. They will continue that process today and begin unlimbering the craft's instruments to look at the soil in the immediate area of the lander.

The rover will spend at least three days in its present location, about 2 1/2 feet from the lander, using its microscope to image the soil and allowing engineers on Earth to practice with the other instruments. The craft will then take off on its excursion at the stately pace of about 1 1/2 inches per second. Its first major goal will be a 200-yard-wide crater about 800 feet to the northeast.

Along the way, it will visit two large rocks, about 15 feet from the rover, that the team has named Adirondack and Sashimi. If there is time, it will also visit a large depression dubbed Sleepy Hollow.

Once the craft has visited the crater, which will allow it to look into the interior of the planet, it will head east toward a complex of hills about 1.8 miles away.

Spirit's twin, Opportunity, is scheduled to land Jan. 24 on the opposite side of Mars in Meridiani Planum.