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?

The skill and success of the mission cannot be underestimated. Landing on Mars has proved notoriously difficult. Five of the previous 11 attempts have ended in failure, including the ill-fated British Beagle 2 craft, which disappeared on entry into the thin Martian atmosphere. Phoenix, as its name implies, was built largely from components of an earlier mission aborted after the loss of a previous polar landing mission. It was sent to the pole because all the geological evidence, as well as close observations by flyby orbiters, suggest that huge amounts of ice lie just beneath the surface. And if there is residual water, even in frozen form, there may well be microbes, dormant or in suspended animation.

Like Viking Explorer, Phoenix is designed to scoop up soil samples and analyse them in a mass spectrometer. But this craft has a longer and more powerful arm, which can dig to a depth of 20 inches. It will function for three months, but, given the robustness of earlier space probes, may well continue working for long after that.

Phoenix has rekindled some of the excitement and wonderment generated by earlier space probes. This is important. For engineers and scientists at Nasa and at the feisty Jet Propulsion Laboratory in California depend hugely on public interest and support to underpin the very high costs of space exploration. A steady stream of images, such as those sent back by the magnificent Hubble telescope, have kept public attention focused on the frontiers of astronomy while providing physicists with data essential to quantum research. It is also vital to demonstrate that, while they may be less glamorous than putting humans in space, unmanned missions are hugely innovative and relatively cheap. In recent years such probes have taken exploration to Saturn and its main moon Titan, to Venus, Mars and the outermost reaches of the solar system.

Nasa now believes it is time to return to the Moon. Amazingly, it is more than a generation since that “giant leap for mankind”, and technology has since opened up huge new possibilities for lunar exploration. The greater challenge, however, is something that, given today's financial and technological constraints, still seems unachievable: a manned mission to Mars. How a human body can survive a two-year journey in weightlessness or the radiation of solar flares is still to be resolved. Some space scientists believe this is a fruitless enterprise, and that money would be better spent on unmanned probes that are steadily revealing so much about our universe. But reaching beyond our grasp has always led us further into space. The aim of manned flight should not be abandoned. First, however, scientists should focus on the vital data Phoenix and other probes can provide to make it possible.