"The rover now stands at its full height and all six wheels are in position for driving on the surface of Mars," mission manager Jennifer Trosper said from NASA's Jet Propulsion Laboratory in
Pasadena, California late on Saturday.
The rover spent its seven-month journey to Mars scrunched inside its transport vehicle, but has now completed "a sort of reverse robotic origami," said Chris Voorhees, the engineer in charge of the vehicle's unfolding.
Scientists now estimate Spirit could begin its Martian journey by late Tuesday or early Wednesday - aimed at looking for traces of water on the Red Planet, a possible sign of life - after problems deflating an airbag forced NASA to postpone its exit from the landing platform.
Now they say they can rotate the robot 120 degrees to the right to avoid it getting tangled in the remains of an airbag that cushioned its landing.
They will do that after first commanding the rover to sever
connections between the middle wheels and the lander. Another step - tilting the landing platform to help the robot drive off - has now been deemed unnecessary.
Meanwhile, Spirit continues to send colour images and other
information about its landing terrain in the Gusev Crater. NASA has been processing the images to make high-resolution colour mosaics, the most detailed images ever taken of the red planet.
Spirit landed on Mars on 3 January and began transmitting high-resolution color images back to earth 24 hours later.
A second probe named Opportunity is expected to arrive on Mars during the night of 24 January to join in the mission.
Powered by solar energy, the robots will be able to move 40 metres each Martian day, more than during the entirety of NASA's 1997 Pathfinder mission, with its 10-kilogram mini-robot Sojourner.