Lost in space: the signal from our mission to find life on Mars

They looked exhausted, dejected and disappointed. After an all-night vigil with little or no sleep, the British scientists hoping to land a space probe on Mars were told at just after 6am on Christmas morning that - sadly -their baby had not cried in the night.

American scientists had failed to make contact with Beagle-2, which they should have done if the British-built probe had landed safely in the early hours of yesterday morning. The all-important call sign, in the form of a nine-note tune composed by members of the pop group Blur, had not arrived.

It was bad news because a failure to make contact with Beagle-2 could mean it had fallen into a rocky crevice or even crash landed, making any further attempts at contact futile.

Professor Colin Pillinger, the man who first conceived the idea of sending a robotic lander to look for signs of life on Mars, put on a brave face and insisted that this was just a setback rather than the end of the most ambitious space mission ever undertaken by British scientists.

"At the present time we don't have a signal from Beagle-2 and there is no sign of a signal," he said at an early-morning press conference in London. "We're not yet giving up any hope for Beagle-2. There is a long way to go and there are still many things we can do."

If all had gone to plan, Beagle-2 should have entered the Martian atmosphere at 2.47am yesterday morning with its heat shield protecting its delicate instruments from the searing 1,700C temperatures of atmospheric entry.

Less than three minutes later, an explosive mortar should have deployed Beagle-2's pilot parachute, followed a few seconds later by the main parachute, which should have slowed the descent even further. At 2.51am, a radar altimeter on board the probe should have begun measuring its altitude to gauge when to inflate the three giant gas bags that would cushion the impact of the space probe on landing.

A minute later, if all had gone to plan, Beagle-2 should have literally bounced on to Mars - the first of more than a dozen bounces - before finally coming to a halt to allow the gas bags to split apart and the probe to drop the final metre to land directly on the planet's surface.

Once there, Beagle-2's lid should have opened like a pocket watch to reveal its solar panels and, most critical of all, position its transmitting antenna inside the lid to allow the probe to communicate with a passing spacecraft orbiting overhead.

Any one of these many procedures were, in the jargon of space science, "single-point failures", meaning that if they did not work, the entire mission was lost.

Beagle-2's transmitting antenna emits a signal with the power of about five watts, equivalent to the base-station signals emitted by a mobile phone, and it is designed to communicate soley with an overhead Martian satellite. "The way Beagle-2 has to communicate with Earth is via an orbiting space craft," said Professor Pillinger, a planetary scientist at the Open University who has helped to analyse samples of Moon rock collected from the Apollo lunar missions.

"When the orbiting spacecraft comes over the horizon it starts to transmit a 'hail' - it starts shouting, 'hello Beagle, if you are there, answer me'. And if Beagle hears that signal it sends back a signal," he said. It fell to an American spacecraft called Odyssey to be the first to try to detect Beagle-2 but unfortunately this first attempt yesterday morning failed, although Professor Pillinger pointed out that this in itself does not mean that Beagle-2 was not trying to communicate.

He said there were at least five possible reasons why Beagle-2 failed to communicate with Odyssey. One is that the probe has landed in an unexpected place so that the two spacecraft missed one another.

"The most obvious explanation is that Beagle-2 is down on the surface of Mars but it is not in the place we think it is. And if it's not in the place we think it is, then Odyssey and Beagle- 2 would have tried to talk to each other at the wrong time," Professor Pillinger said.

Alternatively, Beagle-2 may have landed on a rock and its antenna could be tilted at the wrong angle, or its clock may have stopped and then re-started. "The timing could be completely wrong, if the computer had a glitch and restarted the clock after we got down on the surface of Mars then again we could be hailing each other at the wrong time," he said.

Another possibility is that the communications between Beagle and the American Odyssey - operated by the US National Aeronautics and Space Administration (Nasa) - failed because of software incompatibility. "We didn't do a deal with Nasa until after Odyssey had taken off and so we didn't have any opportunity whatsoever to test end-to-end the two systems. So there could be some incompatibility between the two. We always realised this was a possibility," Professor Pillinger explained. To some extent none of these scenarios would be a total disaster, but there is a final possibility that would spell the end. "It is of course that something in the entry, descent and landing system failed. There are plenty of places where that could have happened."

One consolation yesterday was the news that Beagle-2's mother ship, Mars Express, had successfully entered orbit around Mars. On 4 January Mars Express is scheduled to enter an orbit suitable for direct contact with its baby probe on the Martian surface.

Until then, scientists will continue to attempt direct contact with Beagle-2 using the Jodrell Bank radio telescope in Cheshire which is powerful enough to listen to a 10-second unmodulated call sign of Beagle which it emits during daytime on Mars when all other systems are shut down and in safe mode.

But even if Jodrell Bank detects Beagle-2's transmitter, it will be unable to send the necessary commands to direct the probe's sequence of life-hunting experiments.

"If Jodrell gets a signal that it's alive then there's enough computer programming there for Beagle to stay in hibernation until we can try other Odyssey contacts or Mars Express contacts," Professor Pillinger said.

As Jodrell Bank began its search for Beagle-2's faint signal late last night, the man whose vision made it all possible was sanguine about the degree of success so far. "Nobody could have worked harder than this team to get it right. No amount of money would have made this team work any harder than they did. Everybody on this team did everything that they possibly could to get this spacecraft to Mars," Professor Pillinger said.

"Ultimately there's a point when you can say we have no idea where this spacecraft is and the transmitter goes into auto mode and it tries to turn itself on at regular intervals in the hope that somebody somewhere will detect it, but we haven't got to that stage yet."

"The good news is that Mars Express is safely in orbit. There are at least three British experimenters who are already celebrating a merry Christmas. The rest of us are not downhearted yet. I'm afraid it's the usual England scenario - we're in extra time."

The waiting continued today. After a fruitless night, Prof. Pillinger said the search would continue and that he remained hopeful of success.

IMAGINARY WORLDS SWEPT AWAY BY SCIENCE

By Brian Aldiss

I still remember the day I discovered that travel through space was possible. It was Christmas Day, possibly 1935. My best present was Modern Boy's Annual. In it was an article on how a space rocket should be propelled, launched from a site as near the equator as possible, to take advantage of the rotation of the Earth.

It was this last detail which caught my imagination. It sounded so practical. I was 10 years old. From then on, I was a strong advocate of space travel. Assuming the British-made Beagle-2 has landed intact on Martian soil - or regolith, as it is properly called - and contact can be made, the search for life there will begin in earnest. Dead life, of course; Mars's very own contradiction in terms. Even a fossilised single-cell organism would be welcome.

How it has all changed. Edgar Rice Burroughs's Barsoom, the Mars of many of ERB's adventure stories, HG Wells's vampiric monsters of War of the Worlds, Philip K Dick's Mars divided up into UN sectors in Martian Time-Slip - all these alluring imaginary worlds have been swept away by science. When I read the Modern Boy article, I knew nothing of Konstantin Tsiolkovsky or the other theoreticians who helped to make space travel real. Tsiolkovsky was the Russian who understood that for space travel you needed liquid propellants.

I read, and still venerate,Sir James Jeans, that great populariser of astronomy. In his bookThe Mysterious Universe he raises a question still teasing us: Are we alone in the universe? This is the problem that Beagle-2 hopes to resolve. After pointing out the narrow limits from the Sun in which biological life can hope to survive, Jeans says: "It seems incredible that the universe can have been designed primarily to produce life like our own ... surely we might have expected to find a better proportion between the magnitude of the mechanism and the amount of the product ..."

The old Mars is extinct, gone with the scientific wind like other staples of boys' stories of old, such as the dinosaurs which survive deep in the Amazon and the Sargasso Sea, where frog people live on old Spanish galleons. The adventure of Mars now lies within the philosophical question: Are we alone? We may hope that Beagle-2 will tell us if there was life of a kind on our nearest neighbour in space.

But we are looking from the teeming abundance of our world with its great oceans, to a shrunken world covered in desert. There may be subterranean water, an essential for life; but were there ever beings with whom we might have held a conversation? If there was once life on Mars, how did it arrive there? Where else is it to be found? Would we be advised to look for it?

Whatever this good second Beagle discovers, we shall surely find that every answer raises another question. Whether we are alone or not alone in the universe, we still have to discover what kind of creatures we are.