By Laura Miles

Astrobiologists are to test whether life from Mars could have survived a journey to Earth by hiding inside meteorites.

Scientists from the Stone group, including Professor Colin Pillinger of the Open University and Professor Howell Edwards at the University of Bradford, will send bacteria into space and back inside manmade "meteorites" attached to the heat shield of a Russian space probe, Foton 12.

A preliminary experiment took place in September using rock samples that did not harbour bacteria. These showed the physical and chemical changes that took place after entry into the Earth's atmosphere.

The Foton 12 was launched from the Russian cosmodrome Plesetsk on 9 September with three stowaway meteorites. The 2.3 metre-high capsule maintained a low-Earth orbit (300 km) for two weeks while performing experiments in microgravity conditions. It landed safely landed back in Russian territory on 24 September.

Artificial meteorites

The three samples that took the trip to space included a piece of dolomite, a piece of basalt and a manmade piece simulating a sedimentary rock from the Martian surface.

Sedimentary Martian meteorites have never been found on Earth - they are thought to disintegrate during atmospheric entry or shortly after impact.

The results of this pilot experiment are currently being analysed. Preliminary results suggest clear differences between the exposed side of the samples and the side protected by the heat shield.

Dr Andre Brack, of the Centre de Biophysique Moleculaire, Orleans, France, who heads the group, said: "Artificial meteorites offer the possibility of identifying changes accompanying atmospheric entry.

"The next experiment will use samples loaded with bacteria to evaluate the chances of extraterrestrial microbial samples safely reaching the Earth's surface."

The next launch is planned for 27 January, 2000, using a German re-entry capsule launched by the Russian space authorities. This capsule is scheduled to orbit the Earth five times during an eight-hour flight.