Curiosity rover due to land on Mars on Monday

An engineering model of NASA’s Curiosity rover

NASA’s Curiosity rover is on track to land on Mars on Monday to start searching for clues about possible past life in a crater that might have once been filled with water.

Curiosity's target is Gale Crater, near to the Martian equator, where there are geological signs of past water. The plan is for the £1.59bn six-wheeled machine to land as close to Mount Sharp, a 5.5km peak in the centre of the crater with clay deposits around its base, as possible. 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.
However, Curiosity’s landing on the Red Planet is a challenge that has tested the best brains at 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 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 will explore its surroundings on Mars for one Martian year, or 98 Earth weeks, 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 30ft 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 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."
Hundreds of scientists will work together round the clock during the mission, 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.
Curiosity is twice as long and five times as heavy as the twin rovers Spirit and Opportunity, which landed on Mars in 2004.