An exploratory vehicle has landed on Mars this morning in an attempt to find clues to life on the Red Planet.
The six-wheeled robot, Curiosity, landed safely on the planet's surface at 06.33 am.
Two thirds of Mars missions to date have failed, including Britain's ill-fated Beagle 2 lander which was lost on Christmas Day 2003.
But none has been as complex and daring as the Mars Science Laboratory (MSL) mission, which aims to deliver the largest rover to land on the Red Planet.
Curiosity, costing £1.59 billion, is twice as long and five times as heavy as the twin rovers Spirit and Opportunity which landed there in 2004.
I'm safely on the surface of Mars. GALE CRATER I AM IN YOU!!! #MSL
Because of its size and weight, getting the vehicle on to the Martian surface presented a major challenge to scientists at the American space agency Nasa.
The dramatic solution involves dropping the robot on nylon tethers from a hovering "sky crane".
Curiosity's target is Gale Crater, near the Martian equator, where billions of years ago there may have been a large lake.
"Touchdown confirmed, we're safe on Mars. It's time to see where Curiosity can take us."
There was a moment of calm before NASA exploded in to cheers and shouts as the Curiosity lander made its successful landing on the surface of Mars:
The rover was due to land close to a Mount Sharp, a 5.5 kilometre peak in the middle of the crater with clay deposits round its base.
Curiosity bristles with sophisticated instruments designed to discover if Gale Crater could ever have supported simple life.
For one Martian year - 98 Earth weeks - the rover will explore its surroundings using a robot arm to scoop up soil and drill into rock.
– John Bridges, University of Leicester
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.
It also carries its own laser gun for "zapping" rocks up to 30 feet away.
The laser will vaporise tiny amounts of material in a flash of light that can be analysed to reveal chemical data.
As well as carrying a stereo camera for panoramic shots, Curiosity has a magnifying imager that can reveal details smaller than the width of a human hair.
Samples will be analysed using a state-of-the-art onboard laboratory.
The landing site bears geological signs of past water, including what appears to be a lake bed on the floor of the crater.
Channels that may have been carved by flowing water have also been identified.