A US space agency probe has sent back its first images of Mars within hours of arriving on the planet.
The images confirm the rover is in working order
The Spirit rover survived the perilous plunge through the Martian atmosphere after a seven-month voyage from Earth.
The six-wheeled robot will seek signs that Mars was once capable of supporting life.
A second rover, named Opportunity, is expected to land on the other side of the planet at the end of January.
The pictures show the barren, rock-strewn landscape around the rover.
"The images are outstanding," science manager John Callas said. "The quality [is] the best that has been taken. This is incredible. This could not be better."
The six-minute descent to the surface was the most daunting leg of the 500-million-kilometre journey.
In the past, two out of three attempts to land spacecraft on the Red Planet have failed.
The European Space Agency is still searching for the missing British-built Beagle 2 lander.
The probe was supposed to touch down on Mars on Christmas Day but has not yet sent back a signal to confirm it has arrived safely.
Such are the risks of landing on Mars that Nasa installed a system on the rover to send back information about the descent.
The landing sequence took the spacecraft from 19,000 km/h (12,000 mph) to a complete stop in six minutes.
A series of tones picked up by telescopes on Earth signalled that the vehicle's parachute and landing airbags had deployed properly.
Mission controllers at Nasa's Jet Propulsion Laboratory (JPL) in Pasadena, California, smiled and cheered as the news came in.
After a nervous wait of about 20 minutes they received a radio signal from the rover confirming it was functioning after bouncing to a halt on the Martian surface.
Nasa chief Sean O'Keefe congratulated mission officials while scientists jumped up and down in jubilation.
"This is a big night for Nasa - we are back!" he said at a triumphant news conference. "I'm very, very proud of this team and we're on Mars. It's an absolutely incredible accomplishment."
Spirit is one of a pair of rovers that will seek evidence for water on Mars.
Its twin, Opportunity, will touch down on the other side of the planet in late January.
The £545m rovers will roam the planet and examine rocks in a three-month mission to map out the history of water on Mars.
US MARS ROVERS
Spirit targeted at Gusev Crater, possible ancient lake feature
Opportunity to land at Meridiani Planum, which contains minerals often associated with water
Spirit and Opportunity weigh about 17 times as much as the 1997 Sojourner rover
Mission scientist Dr Steve Squyres, from Cornell University in New York, said Spirit and Opportunity would act as robotic field geologists.
"They look around with a stereo, colour camera and with an infrared instrument that can classify rock types from a distance," he said.
"They go to the rocks that seem most interesting. When they get to one, they reach out with a robotic arm that has a handful of tools, a microscope, two instruments for identifying what the rock is made of, and a grinder for getting to a fresh, unweathered surface inside the rock."
Spirit will explore the Gusev Crater, just south of the Martian equator, which may once have held a lake.
First it will spend a week or more scanning its surroundings and carrying out engineering checks.
Then it will roll off its landing pad and start trundling over the surface of Mars.