Three unknown species of bacteria found in the earth's atmosphere raise the prospect of life in space, scientists said today.

An Indian Space Research Organisation (ISRO) balloon found the bacteria in the upper stratosphere - 25 miles above the Earth's surface. The three species are resistant to ultra-violet radiation.

Although the study does not conclusively state so, it could mean there is life in space.

One of the new species is called Janibacter hoyle, after British astronomer Sir Fred Hoyle. The other two are Bacillus isro, in recognition of ISRO's contribution to the findings, and Bacillus aryabhata, after India's ancient scientist Aryabhata.

The balloon collected air samples at heights of 12 miles to 25 miles above the earth's surface and was later parachuted down to be retrieved.

C B S Dutt, the director of the project, said it had led to the identification of organisms able to live in such hostile conditions.

"The project has led to the identification of living organisms in the stratosphere to our knowledge for the first time," he told the Press Association.

"Before space, the living atmosphere for 20 kilometres (12.4 miles) is called the troposphere. Then comes the lower stratosphere followed by the upper stratosphere. These areas are not congenial for living organisms to survive due to the high level of ultra-violet radiation.

"The normal belief was that it is highly prohibitive for the survival of living organisms," he added.

This was the second such experiment conducted by ISRO. Though the earlier one yielded positive results, the organisation decided to repeat the experiment to ensure it was totally free from any terrestrial contamination.