SAN FRANCISCO --Scientists have revised their thinking in the more than two decades since the Viking missions to Mars sent back no signs of moisture or life on the red planet. Many now believe that perhaps Mars had life that became extinct. They are pinning their hopes on new missions that will once again look for signs of water, underground hot springs and the potential for life.
"After Viking, there was a feeling we had been there, done that, and so much for looking for life," said Jack Farmer, a geologist and paleontologist with NASA's Ames Research Center in Mountain View.
In the next round of explorations, scientists are heading out in search of an ancient biosphere that could be obscured in underground oases that Viking missed or in mineral deposits of now-dry lakebeds and channels.
They'll have a few chances. Although the $1 billion Mars Observer was lost in 1993 before it could radio home some of the answers to Mars' great mysteries, smaller missions are upcoming.
NASA has a Mars Pathfinder mission scheduled for launch in 1996, which will send a small rover to the Martian surface in 1997. It also has Mars Global Surveyor missions scheduled for launch in 1996 and 1998 to make observations of minerals and rocks from orbit.
Russia also plans separate launches.
Scientists are now paying more attention to evidence of the similarities between the geology of Earth and Mars more than 3.5 billion years ago. While life was forming on Earth, they believe there was water on Mars.
"We think there are certain kinds of deposits ... where we can capture evidence of life," Farmer said Tuesday at the American Geophysical Union meeting here.
Knowing that the surface of Mars is below the freezing point of water, scientists now think that the only signs of water they'll see will be from peering below the planet surface, according to several of the 25 Mars-related presentations at the meeting.
One of the biggest goals will be to find geologic evidence of hot springs and channels that could have sustained life. Studies on Earth have shown that certain primitive life forms can survive in the very high temperatures of hot undersea vents, as well as the very low temperatures of frozen tundra and the interior of cold desert rocks.
"A hydrothermal system is inevitable on any planet with liquid water and volcanoes," said Everett Shock, a geochemist at Washington University in St. Louis.
Carol Stoker, a planetary scientist with NASA's Ames Research Center, said upcoming explorations will require sophisticated robotics on rovers.
Terrestrial tests have shown some of their remote-control limitations.
During a test last February on Hawaii, instruments on a Russian rover equipped with the same instruments that will be carried on a 1998 joint Russian-French mission, completely missed a green plant just 6 inches from where they were pointed.
"If you don't look at it, you don't see it," she noted.
Original file name: .CNI - Life on Mars?
This file was converted with TextToHTML - (c) Logic n.v.