After a nine-month, 423 million-mile flight, a tiny automated science laboratory touched down in the early hours of Sunday on the frozen desert around the north pole of Mars, ready to begin the search for water and assess whether there is, or ever has been, life on the Red Planet. Thirty-two years since Viking Explorer first landed under a salmon-coloured sky, the world has again been astonished by the spectacular pictures sent back from a silent valley floor in this dry, ghostly world. Scientists at the Nasa control centre were ecstatic. Not only had the Phoenix spacecraft made a perfect landing after a series of failures; but its sophisticated technology is now ready to shed light on one of mankind's oldest questions: does life exist only on Earth?