Many feared that this landing system, which had never been used before, was simply too complicated, and that the $US2.5 billion mission could fail. But the doubters - myself included - have been proved wrong. What a view ... An image taken by NASA's Curiosity rover showing Mars' Mount Sharp in the distance. Credit:NASA "Touchdown confirmed," said engineer Allen Chen at the jet propulsion laboratory (JPL), NASA's planetary science headquarters. "We landed in a nice flat spot. Beautiful, really beautiful," said engineer Adam Steltzner, the man in charge of the landing. So much was hanging on this mission that some people at JPL were nearly physically sick, and at one point the centre's director, Charles Elachi, had to plead for calm. After the first test pictures came through from the Martian surface, President Barack Obama lauded the success as "an unprecedented feat of technology that will stand as a point of national pride far into the future". So what does this mean for our understanding of the Red Planet? First, it cannot be stressed too highly that this was make or break for NASA. Last year saw the effective cancellation of the manned space program with the retirement of the shuttles. If Curiosity had ended up as scrap metal, NASA's planetary science division would have been humiliated, and any requests for funding for future missions would probably have been refused.

Indeed, according to Mars expert Bob Zubrin, the loss of Curiosity could have meant effectively an end to the US venturing into space for at least a generation, and the keys to the solar system would have been handed to the Chinese. But for now, the Red Planet is firmly in American hands. Touchdown ... In this image, NASA's Curiosity rover and its parachute, left, descend to the Martian surface. Credit:NASA/AP This is NASA's seventh successful landing on Mars: the first two landers, Viking 1 and Viking 2, touched down in 1976. Since then more landers, including the two large rovers, Spirit and Opportunity, which touched down in 2004, have revolutionised our view of this alien world. Ever since mankind turned our telescopes on the fourth planet in the 17th century, arguments have raged over what kind of world Mars is. Importantly, aside from the moon, it is the only celestial body whose solid surface can clearly be seen from Earth. First look ... One of the first images taken by Curiosity shows the rover's wheel on Martian soil. Credit:NASA

Early on it was clear that Mars had ice at the poles and changed colour on a seasonal basis. It had a day just 30 minutes longer than ours, and well into the 20th century most astronomers assumed that Mars was fairly Earth-like and probably home to some sort of life. The most enthusiastic proponent of "a living Mars" was astronomer Percival Lowell, who in the 1890s at his observatory in Flagstaff, Arizona, spent night after night observing his beloved Mars. He saw, or at least thought he saw, a network of canals on the surface, which he reasoned had been built by Martians to irrigate their arid equatorial regions. But talk of canals vanished with the arrival of the first space probes in the 1960s, which showed an arid cratered surface, no canals and certainly no Martians. Isn't she lovely ... Mars, as pictured by the Hubble telescope in 2003. Credit:NASA/AP The loss of Curiosity could have meant effectively an end to the US venturing into space for at least a generation, and the keys to the solar system would have been handed to the Chinese. But for now, the Red Planet is firmly in American hands. What is interesting is how far the pendulum has swung back since - away from Mars as a lifeless, airless lump of rock much like our moon, towards something more like Lowell's view of the place. There are no canal builders perhaps, but we now have the sense of an active world with mighty volcanoes and a surface covered with evidence that this planet once had huge rivers, lakes and even seas.

Observations from orbit, including those from the Mars Global Surveyor, have shown evidence that liquid water may flow on Mars today. What we don't know is whether there is or has ever been life on Mars. Fifty shades of red ... In this image released by NASA, a green diamond shows approximately where the Curiosity rover landed on Mars, a region about two kilometres north-east of its target in the centre of the estimated landing region (circled in blue). Credit:NASA/AP The Viking landers had equipment that watered and fertilised the soil to see if any microbes might be lurking there. The results were inconclusive although some scientists - including the man who defined the experiment, Gil Levin - insist that Viking did find evidence for life. Spirit and Opportunity were not equipped for life detection experiments but they found that Mars is made of a wide variety of rock, including sediments that were laid down in an aquatic environment. Curiosity too is not equipped to find life directly (except perhaps the sort that would come and wave at one of its 17 cameras) and this is something that has been met with raised eyebrows. A few years ago, I asked Mike Meyer, head of Mars exploration at NASA, why he would spend all that money sending a robot the size of a large car to Mars and not look for life directly, merely evidence for conditions that are or were life-friendly. He replied that since we have no idea of what Martian life may be like, searching for it would be like looking for a needle in a haystack. Nevertheless, many scientists, including Britain's Colin Pillinger (the man behind the doomed Beagle 2 mission to Mars), think that life detection should be a priority.

This niggle aside, Curiosity is a fabulous beast. Nuclear-powered, its plutonium batteries provide enough juice to keep it trundling around at a stately 160 metres an hour for maybe a decade or even two. During this time, it will have the opportunity to poke, prod and zap with its laser the complex suite of rocks in Gale Crater and maybe even to climb the mighty five-kilometre high Mount Aeolis (also known as Mount Sharp at NASA) which lies in its centre. In the coming days, expect to see hundreds of stunning images showing landscapes far more dramatic than we have seen before. In the next six months Curiosity will tell us more about Mars than we have learnt in the last 40 years. When humans eventually visit, towards the end of this century, they will arrive at a world that will be familiar. Loading NASA spoke of its seven minutes of terror on Sunday night as Curiosity came shrieking through the Martian air like a man-made meteor. It now looks forward to many years of quiet satisfaction and scientific intrigue as this most extraordinary of envoys from humanity undertakes its Olympian exploration of the red world. - The Telegraph, London