Was there life on Mars? Tune in to find out

A NUCLEAR-powered vehicle with its own laser beams is set to land on Mars tomorrow in the most ambitious effort yet to find out if there was once life on Earth's neighbour.

But Nasa engineers will first have to go through "seven minutes of terror" as the one-ton Curiosity rover is lowered from a rocket to the Martian surface by tethers: an untried system that its own designer admits "looks crazy".

Nasa's final grand mission to the planets for years to come, the R21-billion project is supposed to pave the way for human landings - although experts fear that failure could also just as easily scupper Mars as a destination for astronauts.

The Red Planet has proved a deathtrap for space missions. At least half a dozen smaller landers have been "lost", and two dozen satellite missions failed.

In one notorious case, the Mars Climate Orbiter fell to the "Martian curse" in 1999, when one set of US mission programmers used imperial units while another used metric, causing the spacecraft to fly too low and fall under the pull of the planet's gravity: a R2.5-billion foul-up.

Tens of thousands of Americans are expected to watch the landing tomorrow based on a publicity campaign featuring Star Trek's William Shatner, and the promise of truly exotic pictures from Curiosity's 17 remarkable cameras.

The mission's advanced guidance and landing systems mean it can land in the place most dreamt-of by scientists: the deep, 150km-wide Gale crater near the planet's equator, and the bizarre, 5km-high mountain at its centre.

"Mount Sharp" is believed to hold a scientific treasure trove, with exposed bands of rock telling the story of different Martian ages - perhaps including an age in which simple life forms existed there.

Curiosity is headed there because of a common-sense conclusion: that, even on other planets, water flows downhill. Scientists have already proved that water once flowed on Mars. Curiosity's main job is to find evidence of carbon-based molecules - the stuff living things can't exist without.

Doug McCuistion, director of Nasa's Mars Exploration Programme, told the Sunday Times : "Curiosity is a bold step forward in learning about our neighbouring planet. This mission transitions [our] emphasis from the planet's water history to its potential for past or present life."

The previous Mars rovers Spirit and Opportunity - small gizmos that carried just 5kg of science gear each - landed on the planet in a cocoon of air bags, and were powered by solar panels. At the size of a car, and bearing 15 times more weight in equipment, Curiosity must be powered by nuclear batteries, and will rely on an astonishing series of manoeuvres to safely go from 18 000km/h to a gentle landing in seven minutes.

The most controversial is the final "sky crane" trick, in which the rover is supposed to be lowered beneath the rocket engines of its own mother craft by nylon tethers. When the spacecraft above senses that Curiosity has landed, it is supposed to zoom away and crash at a safe distance.

Adam Steltzner, a member of the Nasa team that developed the system, said: "We know it looks crazy [but] it is the result of careful choices."

Another Nasa administrator, John Grunsfeld, said that "the Curiosity landing is the hardest Nasa mission ever attempted in the history of robotic planetary exploration".

Curiosity carries 10 major scientific tools - but the instrument drawing most public interest - besides the high-resolution colour cameras - is its powerful "ChemCam" laser, which can zap rocks from 8m away, and accurately analyse the resultant puff of smoke .