A momentous day has come and past. On August 27, 2003, Earth was nearer to Mars than it has ever been in the past 60,000 years. Despite it being cloudy in Britain, the newspapers were full of how to make the most of this opportunity. It was impossible to watch or hear a weather forecast without the presenter reminding us not to miss the chance of looking at the red planet.

Would all this coverage have been given if Britain had not been going to Mars? I think not. When Mars was close to Earth (in opposition) in 1989, 1971, 1956 and 1939, its spectacular brightness hardly merited a media mention. You have to go back to the oppositions of 1924 and 1909 to find a similar amount of interest.

Now, in 2003, Europe, through the European Space Agency, has an orbiting mission on the way to Mars called Mars Express (MEX). Britain has provided the tiny lander Beagle 2, named in honour of the HMS Beagle, which carried naturalist Charles Darwin on the voyage that led him to write Origin of Species. And that is the point: Beagle 2 is going to Mars to search for past or present life; to discover if evolution has extended to a second planet in the solar system. Missions from other countries are going too, but they are looking for the ingredients of life, such as water, or to see if the conditions appropriate for life existed in the past. These goals are not the same as that of Beagle 2, which could be the spacecraft that shows we are not alone in the universe.

Beagle 2 is carrying equipment for the method used to show that life on Earth started nearly four billion years ago. In a single experiment using a gas analysis package and involving a mass specrometer the lander will try to find the mineral carbonate (limestone or chalk), which is deposited from water, to see if it contains the bodies of organisms that lived in the water. Finally, it will attempt to show that biology was implicated by recognising the different use of carbon isotopes by the inorganic and organic worlds.

The experiment has been conducted more than 10,000 times on Earth using samples from across the geologic record to show that life began eons ago as soon our planet became stable enough to support it, and that it has followed the same rules ever since. It’s the most general way we can think of to look for past life on Mars.

The same experiment has also been performed on Earth on Martian meteorites, suggesting there is a good chance of successfully recognising past life on Mars. Although the meteorites contain organic matter, it isn’t possible for anyone to honesty say it comes from a Martian organism as it may have been colonised after the meteorites got to Earth. With something as important as discovering life beyond Earth, we have to be doubly sure.

Beagle 2 is going to Mars to repeat the experiments performed on Martian meteorites to exclude the argument that the evidence of life was acquired as terrestrial contamination. It intends to characterise the samples studied chemically and mineralogically to ensure that any results it gets are not considered out of context. It has an X-ray spectrometer to provide major, minor and trace element data, a Mossbauer spectrometer, which distinguishes between minerals containing iron, and a microscope for close-up inspection of samples. Even if evidence of life is not found, the data will be immensely valuable.

The way Beagle 2 intends to look for current life is even more general. The Open University’s mass spectrometer will scrutinise the atmosphere for traces of gas that should not be there unless their continual production by biology is a sustainable source. Analysing the atmosphere means the lander doesn’t need to be particularly accurate where it goes, nor does it need to have a vehicle that moves around. The atmosphere circulates past it, so it just needs to capture some and process it. The objective is to find methane, which is the product of the simplest metabolic reaction. The metabolism could be on the other side of the planet, taking place 1,000 metres (3,300ft) down, but Beagle 2 will still recognise its waste products blowing in the wind.

On August 27, the closeness of Mars signalled Beagle 2 was almost half way there. According to a poll conducted by the European Space Agency, 69 per cent of Britons are aware of this and are awaiting Christmas morning with more than the usual anticipation. Beagle 2 is scheduled to land at 2.54am when only late-night revellers and those prepared for an all-night vigil should be about. At the Open University we know who our fans are from the Beagle 2 postbag. It’s mums and dads, grandparents and children, science and engineering societies, schools and clubs. They are the regular recipients of the Beagle 2 Bulletin (www.beagle2.com). To satisfy demand I have written Beagle - From Sailing Ship to Mars Spacecraft. Little has changed in how to explore a planet in 170 years since Charles Darwin’s global voyage. The National Maritime Museum in Greenwich, London, is holding an exhibition comparing the voyages: “The Beagle Voyages from Earth to Mars” will run until January.

The spacecraft is often described as a large pocket watch and a look inside explains the comparison. Everything, including the mechanical devices and electronics, is tightly packed inside a device the size of a back-garden barbecue. There are 11 kilograms devoted to science in a lander of 33.4kg and a further 35kg dedicated to the landing system. This is the highest density of science to lander-systems mass ever attempted.

Details of Beagle 2‘s educational activities will be announced nearer to the landing. Rehearsals of Beagle 2‘s operations are already on show at the National Space Centre in Leicester (see details at end of article).

Mission control in Milton Keynes - or Beagle 2 Bridge as we like to call it - will hold daily press conferences after landing, explaining how the project is progressing, and will provide a forum for discussion of what it all means in respect of life on Mars. The project promises to be long-running, with its primary mission scheduled to last for 180 days. In the meantime there is still more than 100 million miles to fly. On December 19, Beagle 2 will be woken up and a signal generated by the on-board computer will send it spinning towards Mars’ atmosphere. There will be five and a half days of nerve-racking silence, but come December 25 we should be listening to the nine-note composition by Blur entitled “Beagle 2”, which has been especially written to act as the Beagle 2 call sign and announce its arrival on Mars.

Professor Colin Pillinger is head of the Planetary and Space Sciences Research Institute (PSSRI)at the Open University in Milton Keynes.

The National Space Centre is currently holding rehearsals for Beagle 2‘s landing. These can be watched, but they are unscheduled. However, during November and December the centre will be conducting full-time preparations

Tickets and information: 0870 60 77223; www.nssc.co.uk

National Maritime Museum. Tel: 020 83126565; www.nmm.ac.uk

Beagle - From Sailing Ship to Mars Spacecraft By Professor Colin Pillinger; PSSRITel: 01908 655169; Email: psrg@open.ac.uk