On board the spacecraft Little Prince, three intrepid astronauts are preparing to set foot on a new world. They are the first humans ever to have travelled this far from Earth, and their home planet has shrunk to a pinprick of faintly bluish light behind them. By contrast, their goal looms in the viewports ahead, flooding the cabin with dazzling light reflected from a wild landscape of canyons, deserts and hills. This great conquest stretches almost 60 metres across. Since NASA's Mars programme was cancelled last year, the agency's human space flight efforts have been directed at sending explorers to a passing asteroid. Such a target, announced by President Obama in April 2010, may be small in size, but the rewards could be great. Asteroid-nauts will try to discover what these planetary scraps are made of, whether they helped to start life on Earth 1 and how they can be prevented from smashing into our delicate planet. Fortunately, the objects that present the biggest hazard are also easiest to reach, says Paul Abell, who studies near-Earth objects from NASA's Johnson Space Center in Houston, Texas. "They can come and get us, but we can get to them too."
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