After 36 weeks flying 352 million miles through the interplanetary void between Earth and Mars, Curiosity ended its journey with a perfect landing yesterday morning. Bang on schedule, at 6.32am London time, the one-tonne rover touched down safely on the dust-strewn surface of the Red Planet.
The last leg of the flight, dubbed the "seven minutes of terror", saw its mother spacecraft deploy parachutes, a heat shield, retrorockets and some nifty S-shaped turns to slow it down from the break-neck speed of 13,200mph to land its six-wheeled baby with a gentle bump.
Now a space probe the size of a family car – the biggest to sit on the surface of another planet – is awaiting orders to begin one of the most thrilling assignments in the history of space exploration.
Its bank of 10 scientific instruments are the most sophisticated of any roving vehicle to land on Mars and are designed to find out whether our neighbouring planet was ever habitable. In short, Curiosity could answer one of the biggest questions of science: was there ever life on Mars?
The $2.5bn (£1.67bn) mission was literally hanging by a thread just a few moments before touchdown yesterday as the six-wheeled Curiosity rover was lowered on three nylon lines from its mother spacecraft hovering about 6m (20ft) overhead.
Nasa scientists had taken a huge gamble in using a novel kind of landing device, which they called the "sky crane", because other tried-and-tested methods, such as giant, inflatable airbags to cushion the final bump, would not work with a payload this heavy.
The sense of tension, and then relief, was evident within mission control at Nasa's Jet Propulsion Laboratory (JPL) in Pasadena, California, as the sky crane delivered its precision cargo. Loud cheers broke the tense silence after Al Chen, a JPL engineer, announced: "Touchdown confirmed."
John Holdren, President Obama's chief scientist, immediately trumpeted the American success, which had been likened in its technological precision to driving a golf ball from a tee in Los Angeles to a green in St Andrew's, and still managing to get a hole in one.
"If anybody has been harbouring doubts about the status of US leadership in space, well there's a one-ton, automobile-size piece of American ingenuity, and it's sitting on the surface of Mars right now," Dr Holdren said.
No other nation can claim to have put a spacecraft of any size on the surface of Mars, yet for the US National Aeronautics and Space Administration it was the seventh success out of eight attempts – and technically this was by far the most difficult.
The scientific instruments on board Curiosity are 15 times as large as the science payloads on the two previous Mars rovers, Spirit and Opportunity. Some of them, such as the laser-firing spectrometer for checking the chemical composition of rocks from a distance, have never been used before.
Nasa said that the rover, which is powered by plutonium batteries so that it does not have to rely on solar panels, will use a drill and scoop at the end of its robotic arm to gather soil and rock samples, which will be analysed by an on-board laboratory that will beam the results back to Earth.
The nuclear-powered Curiosity is designed to operate for two years but Nasa scientists are quietly confident that it will still be collecting data and sending it back to Earth in 10 or even 20 years' time.
They landed Curiosity in one of the most enigmatic regions of Mars, a vast depression called the Gale Crater. The rover will spend much of its time exploring the crater's internal mountain where the geological history of Mars can be explored.
Observations from orbiting spacecraft show that the lower layers of this mountain include clay and sulphate minerals, indicating that it has been exposed to liquid water, one of the essential preconditions for life.
Other scientific expeditions on Mars have already shown that there was water on the planet, which is believed to be vital for the origin and evolution of life. Curiosity should be able to discover whether this part of Mars was indeed habitable in the past, or even whether it could support future manned visits, said Nasa administrator Charles Bolden.
"Curiosity, the most sophisticated rover ever built, is now on the surface of the Red Planet, where it will seek to answer age-old questions about whether life ever existed on Mars, or if the planet can sustain life in the future," Dr Bolden said.
Mission control: steering by committee
Driving a car on Mars sounds like the ultimate Jeremy Clarkson experience, but in fact it requires a geek-like understanding of computer programming. Scott Maxell usually drives a Toyota Prius, but he also has the enviable job of driving probably the most expensive wheeled vehicle in history – the $2.6bn (£1.67bn) Curiosity rover.
Maxwell is one of about a dozen Nasa engineers charged with the task of steering Curiosity over the surface of the Red Planet from mission control in Pasadena, California, more than 100 million miles away. He said: "It's a priceless national asset that happens to be sitting on the surface of another planet. You better take that damn seriously."
The 41-year-old has already "driven" 2003's twin Mars explorers Spirit and Opportunity.
As radio signals take from four to 20 minutes to reach Mars, each manoeuvre is painstakingly worked out the previous day and sent as a complete batch of commands.
"It's as if we're e-mailing the rover its To Do list for the entire day," Maxwell said. "You're essentially driving a robot with a keyboard 100 million miles away. If anything goes wrong, there's no one there to hit the panic switch."
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