A one-ton rover as big as a Mini is due to land on Mars on Monday in one of the most daring space missions ever attempted.
The rover, Curiosity, is designed to search for clues about possible past life in a crater that might once have been filled with water.
The six-wheeled machine is twice as long and five times as heavy as the twin rovers Spirit and Opportunity which landed on Mars in 2004.
Two British scientists are members of the team which will direct the rover and analyse the data it collects.
Before they can do their work Curiosity must land safely on the Red Planet – a challenge that has tested the best brains at the American space agency Nasa.
Because Curiosity is so big and heavy, getting it onto the Martian surface has required a great deal of “thinking out of the box”.
The solution is so bold it has been described as “crazy”.
After entering the Martian atmosphere at 13,200mph, the capsule containing Curiosity will be slowed by friction and then a supersonic parachute.
An “upper stage” resembling a flying bedstead will then be deployed, firing retro rockets to brake its descent.
As it hovers over the landing site, the upper stage will transform itself into a “sky crane” and lower Curiosity to the surface on the end of a tether. It will then break away, and deliberately crash.
Statistically the odds do not look good. Two-thirds of all Mars missions have failed, including Britain’s ill-fated Beagle 2, which was lost on Christmas Day 2003.
Dr John Bridges, from the University of Leicester Space Research Centre, one of the British scientists working on the Mars Science Laboratory mission, said: “I’m cautiously optimistic. Space exploration is not for the faint hearted.
“The previous rover landing used inflatable bouncing bags. Curiosity’s just too heavy for that, so they developed the sky crane technique.”
Curiosity’s target is Gale Crater, near the Martian equator, where there are geological signs of past water.
The plan is to land close to Mount Sharp, a 5.5-kilometre peak in the centre of the crater with clay deposits around its base.
If all goes well the radio signal confirming that Curiosity has landed will arrive on Earth after a 14-minute journey through space at 06.31, UK time.
For one Martian year – 98 Earth weeks – Curiosity will explore its surroundings using its robot arm and a formidable array of scientific instruments to analyse samples drilled from rocks or scooped from the ground.
It also carries a laser capable of zapping rocks up to 30 feet away, vaporising tiny amounts of material in a flash of light that can be analysed to reveal chemical data.
As well carrying a stereo camera to take panoramic shots, Curiosity will be equipped with a magnifying imager that can reveal details smaller than the width of a human hair.
Geologist Professor Sanjeev Gupta, from Imperial College London, the other British scientist involved in the mission, said: “Nasa chose Gale Crater as the landing site because it has a number of really exciting geological features that we are hoping to explore. These include a canyon and what appears to be a lake bed on the floor of the crater, as well as a channel and a delta, which we think may have been carved by water.
“We will use the rover’s cameras, including one which is like a powerful magnifying glass, to study the geology up close.”
Dr Bridges and Prof Gupta will be based at Nasa’s Jet Propulsion Laboratory in Pasadena, California, during the mission.
They will be among hundreds of scientists who will work together round the clock analysing data beamed back from Curiosity, planning experiments and guiding the rover’s excursions.
Dr Bridges said a key goal is to study the clay sediments at the foot of Mount Sharp. Scientists believe they are a reminder of a time, three to four billion years ago, when there was abundant water on the surface of Mars.
“The clay layers may represent what we loosely call a warm and wet period in Martian history,” said Dr Bridges. “On the top of the mountain the rock was deposited under dry conditions, so there was a great environmental change.
“There’s this idea that Mars was warm and wet long ago, but we don’t know how long there were standing bodies of water on Mars, whether they were short lived or lasted hundreds of millions of years. That’s important to the question of whether life ever existed there. Although we’ve made enormous strides in understanding Mars over the last 10 or 20 years, there’s still a lot we don’t know.”
An Atlas V rocket carrying Curiosity blasted off from Cape Canaveral, Florida, in November. The journey to Mars crossed 352 million miles of space.