Curiosity, the first fully-fledged mobile science lab sent to a distant world, was scheduled to touch down inside a vast impact crater at 7.31 this morning.

Mission control engineers at the Jet Propulsion Laboratory, near Los Angeles, acknowledge that delivering the 1t nuclear-powered vehicle in one piece is a highly risky proposition, with zero margin for error.

But, on the eve of Curiosity's rendezvous with Mars, the team said the spacecraft and all its systems were functioning flawlessly, and the forecasts were for favorable Martian weather at the landing zone.

Engineers said they hoped that the rover, the size of a small sports car, will land as planned near the foot of a tall mountain rising from the floor of Gale Crater.

"We're right on target to fly through the eye of the needle," Arthur Amador, the Mars Science Laboratory mission manager, said on Saturday.

Facing deep cuts in its science budget, Nasa has much at stake in the outcome of the $2.5-billion mission.

Mars is the chief component of its long-term deep space exploration plans.

The rover is equipped with an array of sophisticated chemistry and geology instruments capable of analysing samples of soil, rocks and atmosphere on the spot and beaming results back to scientists on Earth.

In a good-luck tradition dating back to the 1970s, engineers in the control room at Jet Propulsion Laboratory will break out cans of roasted peanuts about an hour before the landing.