Mars find puts life back into space race

United States President Bill Clinton echoed his forerunner John Kennedy last night, with a promise that the US space agency Nasa will use "its full intellectual power and technological prowess" to search for more evidence of life on Mars.

His statement, reminiscent of Kennedy's historic 1960s pledge to put a man on the Moon by the end of the decade, followed new research from Nasa which suggests that early, single-celled forms of life may have existed on Mars billions of years ago. Mr Clinton said that if confirmed, "it will surely be one of the most stunning insights into our universe that science has ever uncovered."

Excitement about the research, which the agency released in the US ahead of its formal publication next week, spread rapidly worldwide. But scientists and religious thinkers were still digesting the news yesterday that traces of organic chemicals - so tiny that thousands would fit on a full stop - are "evidence for primitive life on early Mars". Religious commentators suggested that initially, at least, it would make no difference to their beliefs.

For scientists, the news could boost funding for space trips to Mars, and lead to international efforts to bring back samples from the planet.

The remains were found in a meteorite and are molecules known as PAHs (polycyclic aromatic hydrocarbons). These could have been made by primitive bacteria and single-celled organisms that might have existed billions of years ago beneath the surface of Mars. PAHs are found on Earth in fossil sediments, where they are formed by bacteria - though independent scientists pointed out that they can be made by inorganic processes too.

A team of six Nasa scientists found the traces of chemicals deep inside the four-billion-year-old rock. "We don't claim that we have conclusively proven [life on Mars]," said one of the scientists, Everett Gibson, at a press conference in Washington. "We are putting this evidence out to the scientific community for other investigators to verify, enhance, attack - disprove if they can - as part of the scientific process."

The work will be published next week in the academic journal Science.

The largest fossil is less than a hundredth of the width of a human hair, and most are about a thousandth of that size. The team said that they are "strikingly similar" to those from tiny bacteria found on Earth.

Nasa already plans a $150m (pounds 97m) trip by an automated spacecraft, Pathfinder, which is due to lift off this November and to land on the planet next July. In 1976, the Viking spacecraft landed in a desert region but found no trace of organic life. Pathfinder, though, will include a remote-controlled vehicle which will be able to examine rocks near the landing site.

The research does not indicate whether any life has survived on Mars. If it has, it is probably deep underground. "We are not talking about little green men," said Nasa's administrator Daniel Goldin.

However, a number of scientists were wary of welcoming the news in advance of the paper's publication. Christian de Duve, a Belgian scientist who is a Nobel laureate and an expert on life in the universe, said yesterday: "Obviously this is extremely exciting news, but I don't like to comment without having more information."

Among religious groups, reactions to the suggestion of life on another planet were mixed. A spokesman for the Catholic Church said: "There is no proof yet but if there were, then it would cause some sort of rethink." A Church of England spokesman said: "We believe that God created the whole universe so I don't think there could be a problem."

Other scientists - including some at Nasa - cast doubt on the findings. Jack Farmer, a geologist and palaeobiologist of the Exobiology Branch of Nasa's Ames Research Center in California, said, "If that's the evidence, I don't believe it ... PAHs have no direct relationship to biology. They are not an indicator."