Nasa to Launch 'Dream Machine'

The vehicle, Curiosity, will launch on November 26, 2011. It has a two-metre arm tipped with a jackhammer and a laser to break through the Martian rock. It can also analyze rock and soil samples with unprecedented accuracy.

The Nasa Jet Propulsion Laboratory's Ashwin Vasavada, deputy project scientist, said: "This is a Mars scientist's dream machine."

Once on the red planet, Curiosity will be on the lookout for organic, carbon-containing compounds. While the rover can't detect the presence of living organisms, scientists hope to learn from the $2.5-billion, nuclear-powered mission whether Mars has, or ever had, what it takes to nurture microbial life.

Doug McCuistion, director of Nasa's Mars exploration programme, says Curiosity will be "the largest and most complex piece of equipment yet placed on another planet".

At two metres long, 2.75 wide and two tall, the Curiosity is twice the size of previous rovers Spirit and Opportunity. It weighs a ton and is loaded with instruments. Its formal name is Mars Science Laboratory (MSL).

In a spacecraft first, Curiosity will be lowered to Mars' surface via a jet pack and a tether system similar to the sky cranes used by helicopters to insert heavy equipment in inaccessible spots on Earth. No bouncing air bags like those used for the Mars Pathfinder lander and rover in 1997 and for Spirit and Opportunity in 2004 - Curiosity is too heavy for that - the kind of precision landing that officials said will benefit future human explorers on Mars.

The rover is scheduled to arrive at the mineral-rich Gale Crater in August 2012, eight months after embarking on the 570 million km voyage aboard an Atlas V rocket.

It's a treacherous journey to Mars, and the road is littered with failures. In all, more than three dozen missions have aimed over the decades at the most Earth-like planet known, and fewer than half have succeeded. Of this flotilla, only one lander is still working on the surface, the Opportunity and only three craft still observe the planet from orbit.

In fact, Russia's latest Mars probe remains stuck in orbit around Earth two weeks after its botched launch. Nasa has had better luck, although it has lost a few spacecraft.

Michael Meyer, lead scientist for the Mars exploration programme: "Mars is difficult, and so many things have to go right for a mission to work."

Curiosity is the capstone of what Nasa calls "the year of the solar system". A spacecraft is en route to Jupiter after lifting off in 2010 from Cape Canaveral, and two probes launched in September 2011 will reach the Moon in December.

huge crowd of 13 500 is expected for Curiosity's send-off.

Curiosity holds 4.8kg of plutonium, more than enough to power the rover on the Martian surface for two years. A nuclear generator won out over solar energy because it allows for a bigger workload and more flexibility. The plutonium is encased in several protective layers in case of a launch accident.

Once safely down on Mars, the rover will survey the landscape with high-definition and laser cameras mounted like eyes on its mast. The laser will aim at soil and rocks as far as 6m away to gauge their chemical composition.

The rover also has a weather station for updates on Martian temperature, humidity and wind, as well as a radiation detector that will be especially useful for planning human expeditions.

Despite all its fancy upgrades, Curiosity will go no faster than the 160 metres an hour logged by previous Martian rovers. It is expected to cover more than 20km during its two-year mission and, if it's still working then, will keep on trucking, possibly all the way up the crater's 5km peak.

This mountain is composed of geologic layers similar to what one might find in the Grand Canyon, said project scientist John Grotzinger, a geologist at the California Institute of Technology.

The next logical step in Mars exploration, said Cornell University's Steve Squyres, would be a robotic mission to deliver Mars samples to Earth for analysis. Nasa hopes to pull that off later this decade but the project is on the US Congress's chopping block.

Squyres warned that without such missions, US leadership in science will not only be challenged - "it's going to go away".