/ 24 January 2004

Mars: Water, river valleys, but was there life?

The European mission to Mars has found the first hard evidence of water on the planet, a discovery which raises questions about the possibility of life on other planets.

Sophisticated instruments aboard Mars Express have identified the telltale signature of water ice trapped amid frozen carbon dioxide over the Martian south pole.

Astronomers have long suspected water in the polar icecaps and an American spacecraft three years ago used indirect methods to detect its presence. But Mars Express has confirmed the find directly and begun the first detailed examination.

Another set of sensors has begun to measure the faintest traces of water vapour and ozone in the upper atmosphere. A third has begun to ”feel” up to 5km below the surface, looking for permafrost, aquifers or even underground rivers.

Mars was once much more like Earth: it had active volcanos and probably a denser atmosphere. It may also have been scoured by seas and rivers. And — if controversial evidence found in 1996 within a Martian meteorite is anything to go by — it may once have been home to life.

One of the most powerful instruments aboard Mars Express is a high resolution stereoscopic camera that has begun to map the surface of the planet as never before, and to build up a three-dimensional picture of the planet’s topography.

The adventure has just begun — but the first images beamed across 100 million miles of space have stunned mission scientists.

”We are not getting yet another boring bird’s-eye view, we are getting exciting 3-D views, particularly of dust rolling over the side of a crater wall,” said Jan-Peter Muller, of University College London, one of the camera team.

His colleague John Murray, of the Open University, said: ”It’s just so beautiful as well as awe-inspiring. It’s a huge achievement. It’s just art and science and beauty and exploration all mixed up together.”

Mars Express arrived on December 25, the day it delivered the British lander Beagle 2. Its camera has mapped an area roughly equivalent to half the surface of Europe. The mission is likely to last a Martian year of 687 Earth days.

Yesterday’s first results brought joy and relief to European scientists. More than half of all missions there in the last 40 years have failed. Yesterday, things looked bleak for Beagle 2, silent since its arrival, and for a while unhappy for the US lander Spirit, which touched down on January 4 but went ominously quiet on its first adventure on Wednesday.

Last August, Mars and Earth were closer than they had been for 60 000 years. A fourth intruder — a US robot rover called Opportunity — will make a landing attempt tomorrow.

Mars Express is making a series of elliptical sweeps over the poles of the planet, surging to within 275km at its closest, and then swinging away to a distance of more than 11 000km as it relays its data back to Earth. On each approach, it has begun to examine the planet’s surface in stunning detail, photographing mesas and cliffs and even the marks left on them by water, including scouring caused by a vanished watercourse.

One image, of a vast caldera in a huge extinct volcano, even seems to catch the reflected light from dust falling off the rim to the crater floor 3km below.

”This is only the beginning. We are just lifting the curtain,” said David Southwood, director of science for the European Space Agency, as mission chiefs unveiled the first results in Darmstadt, Germany. – Guardian Unlimited Â