Tim Radford reports on a new probe of the red planet
British scientists are hoping to land an instrument on Mars that will “sniff” the presence of extraterrestrial life. Beagle 2 – the name evokes Charles Darwin’s world- changing voyage aboard HMS Beagle in 1831 – could be launched aboard a European mission called Mars Express in 2003.
Beagle 2 will weigh just 60kg. It will have a camera and a robotic arm to drill into the heart of nearby rocks. A robot “mole” will burrow under boulders to examine soil chemistry. Its package of X-ray and spectrometry instruments will measure the potassium ratios of the rocks to date them accurately, and look for evidence of organic chemicals and the presence of water. It is hoped it will answer questions about the possibility of bygone life.
But its most sensitive detectors will also sample the thin atmosphere of the red planet for the most tantalising prize of all – methane. Methane is also known as marsh gas or “natural gas”. It is produced by microbes acting as digesters, often in conditions without oxygen.
The process goes on in swamps, termites’ nests and the guts of mammals. To put it at its crudest, scientists on Earth will use Beagle 2 to detect the faintest trace of a fart on a planet across the hugeness of space.
Life keeps the methane content of the air we breathe at about 1,7 parts per million. The Beagle 2 instruments will pick up levels of parts per billion.
“If there is anything, any place on Mars, even somewhere deep down, 2 000km away from our landing site, contributing methane continuously to the atmosphere, then we have a chance of picking it up. I don’t expect there to be very much. But if you don’t find any methane at all then you really have to start believing this is a very dead planet,” said Colin Pillinger, of the Open University.
A Nasa Viking mission more than 20 years ago pronounced Mars a dead planet, with temperatures falling to -100 C. Two years ago, Nasa scientists, peering at a Martian meteorite found in Antarctica, announced that they could see fossil traces of ancient bacteria in the meteoritic rock: evidence of life long ago. Others see the fossils as accidents of rock chemistry. The debate has raged on. Since then, the Nasa Pathfinder mission has confirmed that Mars was once a warmer world, on which water flowed.
“Forget bloody fossils,” said Pillinger. “I believe the conditions on Mars tell us that water has been percolating around less than three billion years ago, and it was warm, and therefore, somewhere nicely hidden away from its oxidising surface, there are environments that may be geothermally heated, that could be niches for life.
“We know now on Earth, 20 years after Viking, that life is much more tenacious than we ever believed. It is able to survive in some horrendous places on Earth, and therefore the chances of finding it on Mars really need to be thought through and tried again.”
There is a catch. The mission is being designed and planned by a consortium from the Open University, the University of Leicester, Matra Marconi Space at Bristol, the Martin-Baker Aircraft Company, the Rutherford Appleton laboratory and others. But it needs a guarantee of 25-million in time to meet the deadline set by the European Space Agency.
The scheme has the implicit backing of Britain’s space scientists. But there is simply no money left in the physics and astronomy budget. The hope is to get direct help from other government sources, or from industrial sponsors, over the next few months.