By ANNE BESTON
Exploring beneath the surface of neighbouring planets and moons is probably not the way to find alien life, a world-renowned biochemist says.
Professor Norman Pace, of the University of Colorado, Boulder, said the chance of finding primitive life in thermal vents on Mars was not promising and the next likeliest place to find it - on the ice on Europa, a moon of Jupiter - was even more of a long shot. "If you look at what is required for life, it really is a narrow window," he told an American Association for the Advancement of Science meeting.
Scientists did not know enough about Mars to have an idea whether primitive life could exist in thermal vents on the red planet.
"Our solar system doesn't seem too promising to sustain life, but we don't know what kind of extreme conditions conducive to life may be found elsewhere," he said.
Primitive life on Earth has been found in boiling thermal vents in the oceans, and microbes have been found in ice, so the temperature span for life anywhere in the universe is likely to range roughly from minus 50 deg C to 150 deg C.
Professor Pace said the physical limits of life were likely to be about the same anywhere in the universe.
But if life was going to be found, it would have to take over and modify the surface of a planet, as it had on Earth.
Primitive life forms in the depths of planets or moons were not likely to contribute to changing the surface.
Professor Pace said that if intelligent life was somewhere in the universe, it could be looking at us, possibly considering Earth as a home.
The definition of life should include self-replication (the mechanism of evolution through natural selection) and probably carbon-based molecules, since carbon was one of the most abundant of the higher elements of the universe.
Scientists dig too deep for aliens
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