PASADENA, CALIF. -- To the relief of NASA scientists, the Spirit rover rolled onto the surface of Mars and trundled across the salmon-coloured soil yesterday for the first time since the vehicle bounced to a landing nearly two weeks ago. The slow manoeuvre was a nail-biting moment for scientists who had feared Spirit might become yet another casualty in the star-crossed history of Mars exploration.
"This is a big relief," said Rob Manning, manager of the entry, descent and landing portion of the mission. "Our wheels are finally dirty."
The vehicle had been perched atop its lander since its arrival on Mars Jan. 3. Yesterday, it finally rolled down a ramp onto the surface of the Red Planet, covering three metres, as planned. The trip took 78 seconds.
Engineers had worried the vehicle might become snagged or damaged on its ramp, making it impossible to complete its mission. Scientists said the roll-off may have been the riskiest step the rover will ever take on Mars.
Engineers and scientists with the U.S. National Aeronautics and Space Administration were misty-eyed as they described the success of the manoeuvre.
"Mars now is our sandbox, and we are ready to play and learn," said Charles Elachi, director of NASA's Jet Propulsion Laboratory.
Spirit is to spend three to four days parked beside its lander, giving it time to perform some preliminary analysis of the soil around it. Then it will set off on a journey to prospect for geologic evidence the now-dry planet was once wet and hospitable to life.
Pictures beamed from Spirit showed its two rear wheels on the Martian soil, with its lander 81 centimetres behind it. Two parallel tracks led away from the lander through the cakey dust.
Originally, Spirit was supposed to roll straight off the lander on its ninth day on Mars. But the now-deflated air bags that cushioned the rover's landing blocked the main ramp, forcing Spirit to perform a 115-degree turn to line its wheels up with a different ramp.
Spirit is expected to deploy its robotic arm and take its first photographs with its microscopic imager today.
NASA then plans for Spirit to begin a trip in the direction of a crater about 250 metres away. Spirit was designed to travel dozens of metres a day.
Either of two rocks, two to three metres from the rover, is expected to be Spirit's first target once it starts rolling again.
The rover might also visit a nearby depression dubbed Sleepy Hollow -- if there is enough time before its twin, Opportunity, lands Jan. 24 on the opposite side of the planet.