Leading article: Still looking for life

The prospect that life exists beyond our planet, as well as a fear of what form it may take, have never lost their hold over the imagination. Once, those longed-for celestial beings took the form of winged gods. Now our hopes are humbler – a speck of living lichen or bacteria would be more than enough. Dare one hope to find the fossil of a larger dead organism, imprisoned for eternity in the unforgiving ice?

So the world catches its breath, awaiting the outcome of the mission to Mars of Nasa's Phoenix Lander, which touched down on the red planet's north pole on Sunday. In the days that follow, the probe will begin the search for traces of those vanished lakes and rivers that, millennia ago, leaked into the planet's thin atmosphere, but which may have left some residue under its frozen poles. Everything depends on what happens when those scoops of soil are warmed in tiny ovens placed inside the spacecraft and the vapours analysed. The fact that there is a race against time adds a filmic quality to the drama of the Phoenix Lander: within three months, the north pole of Mars will be so cold that the instruments will freeze.

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Is the expense of these missions worth it? Of course. At just over $550m apiece, spacecraft of the new generation like the Phoenix Lander are a snip compared with their predecessors.

Three Mars rovers, Sojourner, Spirit and Opportunity, have already done yeoman work in examining the soil of Mars. But it's the ice that holds the potential for a real breakthrough in terms of discoveries. We wish it well, and hope we're not alone.