WASHINGTON (AP -- Aug 10, 1996) -- Mars seems an unlikely place for life.
In fact, the red planet today is downright lethal for creatures that need oxygen to breath and warm, moist places to thrive.
Mars is a barren ball of red dirt and rock, unshielded from deadly cosmic and ultraviolet rays that zap its surface constantly. It is soaked in temperatures cold enough to freeze carbon dioxide and scoured by sand storms that can rage for weeks across the whole planet.
Ice caps cover the poles, towering volcanoes punctuate its vast empty plains and sinuous riverlike channels snake across thousands of miles. And everywhere, like scars from a cosmic pox, are impact craters left from space boulders that pounded, pounded, pounded for eons.
And yet, Mars was not always this way. Once, experts believe, life was possible - and some believe quite likely - on this planet that is most similar in many ways to the Earth.
David McKay of the Johnson Space Center in Houston is leader of a team of NASA researchers that claims to have found evidence of ancient Martian microbes in a potato-sized rock that fell to Earth.
More than three billion years ago, he said at a news conference last week, Mars was warm, wet and nurturing. But after a short period of promise, said McKay, Mars "fell on bad times."
The possibility of life on Mars has intrigued humans for more than 300 years. Early astronomers spotted characteristics that reminded them of home.
In the 1600s, observers determined that Mars had a day of about 24 hours and that it had polar ice caps - just like Earth. In the 1700s, astronomers found that Mars was tilted on its axis and, thus, had seasons - just like Earth. And there seemed to be clouds and the dark areas on the planet were taken to be oceans and seas - just like on Earth.
And in 1878, Italian astronomer Giovanni Schiaparelli spotted a system of what he called "canali" on Mars. Canals meant there had to be intelligent life there, perhaps actual human beings - just like Earth.
"Their idea was not nuts," said Allan Treiman, a Mars expert at the Lunar and Planetary Institute in Houston. "Mars is the most Earthlike of the terrestrial planets. It is just a little smaller than Earth. The temperatures are cold, but not that much colder than some places on Earth. And it had features that looked familiar."
Schiaparelli's findings intrigued Percival Lowell, a 19th century mathematician with the money and the drive to follow his curiosity. He built an observatory on a mountain near Flagstaff, Ariz. and was able to map hundreds of canals on Mars. He became convinced that the features were waterways built by Martian engineers to bring water from the poles down to the great plains.
"It was a natural idea," said Treiman. "This was a time when canals were what civilizations did to their planet.
"It was really Lowell's work that pushed Mars into the forefront," he said. "We all live now in the shadow of his legacy. He was dead wrong. But that's where the real fascination with Mars began."
A lively Mars filled with bizarre or even people-like creatures quickly became the subject of pulp fiction, Saturday movie serials and eventually even television shows.
When robot probes finally went to Mars and sent back close up pictures, there was, some have admitted, a sense of disappointment.
The Viking landers in 1976 showed Mars to be barren and hostile.
Wintertime temperatures, it became known, dropped to a minus 193 degrees F. In summer, parts of Mars could reach a balmy 72, but always the atmosphere was poisonous - 93 percent carbon dioxide.
Orbiting survey craft showed clearly that once Mars had water, perhaps whole oceans of it. It cascaded down from the mountains filled now-dry lake beds, cutting gullies and canyons through the iron-rich red soil.
It was this presence of water that gives hope to the people who seek past or present life on Mars.
Treiman said there is a great deal of doubt about the work of McKay and his team. Some scientists do not believe that the NASA researchers' analysis of material in Mars meteorite actually uncovered the chemical signatures of life or the fossils of microbes.
"What they have done may be wrong, but it is good, careful work and it gives us something to thing about," he said.
Scientists now speculate more vigorously about the possibility of microscopic life living in frozen permafrost under the Martian surface, or perhaps that hot underground pools exist where bacteria could thrive. Suddenly, hope has been revived that maybe Earth is not the only planet with life.
The McKay work also has focused new attention on a spacecraft, the Mars Pathfinder, that is will be launched late this year toward a landing on the red planet. It will land in what appears to be a river delta, a fanlike formation that may have once been the bottom of a lake that collected water flowing from the Martian highlands.
There may, some hope, be moisture there yet.
And if there is water...
"It could be a good place to find life," said Treiman.
Copyright 1996 The Associated Press
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