MARTIAN LIFE THEORY DEFENDED.

Byline: Jon Van Chicago Tribune

Scientists agree that there may well still be living creatures on Mars today - if we could look in the right spot.

The announcement last summer that scientists believe they've found evidence for Martian life on a meteorite carried to Earth has stirred human imagination for new exploration to find and describe such life.

A big reason that more scientists expect to find life on Mars - and possibly on other bodies in the solar system, such as Europa, one of Jupiter's moons - is the continuing discovery of life in extremely harsh places on Earth.

New species of microbes have been discovered in boiling waters under high pressure near volcanic vents at the ocean's bottom, as well as inside superheated volcanic rocks and at spots two miles or more beneath the Earth's surface.

The question of extraterrestrial life is a hot topic in Seattle at the annual meeting of the American Association for the Advancement of Science.

Michael Carr, a Mars expert with the U.S. Geological Survey, said recent discoveries of volcanic activity of Jupiter's moons, as well as the known existence of water and volcanism on Mars, have persuaded scientists that if life can survive under harsh conditions on Earth, it probably will be found under similar conditions elsewhere.

``There's a good chance that life still exists on Mars, but it would be difficult to get to it, far below the planet's frozen surface,'' Carr said.

Communities of microbes have been found living 2 miles below Earth's surface with little or no connection to the surface.

``They live on carbon dioxide and reproduce every 100 years or so,'' said Carr. ``If this happens on Earth, it surely could happen under similar conditions on Mars.''

Christopher Romanek, a University of Georgia researcher who was among authors of the paper that stirred excitement last summer by suggesting a Martian meteorite could contain evidence of life, said subsequent papers by others, pouring cold water on the notion, have not killed the idea.

``It's time to pry the lid off the coffin; our interpretations are still very much alive and doing well,'' Romanek said.

It will take more analysis of the evidence before there is a consensus on whether the disputed meteorite bears signs of alien life forms, he said.

John Kerridge of the University of California at San Diego said he thinks it is likely there is life on Mars, but it is buried below the planet's surface and will be difficult to find.

``I'm skeptical that nature chipped off the right kind of rock on Mars and delivered it to Earth for us,'' Kerridge said. He suggested that expeditions of robots be sent to Mars to search for life after likely sites are picked in missions now under way.

A manned mission to the planet would be a mistake because a human presence on Mars would contaminate it with earthly microbes and forever cloud the possibility of finding indigenous life there, he said.

Not all scientists are convinced it will be terribly difficult to find life on Mars.

Thomas Gold, Cornell University professor emeritus of astronomy, said signs of microbial life have been found as deep on Earth as anyone has ever dug, some 6 miles down or so. Mars and other planets likely also harbor subsurface life of one form or another, he said.

``It is very likely that we will find a deep, hot biosphere on Mars, as we have found on Earth,'' said Gold, ``and probably on many other planetary bodies in our solar system.''

While Gold's views are controversial, his arguments and evidence have caused geologists to reassess some long-held views, said the Geological Survey's Carr.

John Baross, a University of Washington oceanographer, is among experts on peculiar forms of life that live in extremely harsh circumstances on Earth. It is probable, he said, that microbes found in high-temperature, high-pressure places, near volcanic vents under the sea, are ancestors of all life forms today, ``including everything from cows to tomatoes.''

And while researchers talk of sending probes to Mars in search of life, Baross noted that there is much unexplored life still lurking in the Earth.