David Perlman, Chronicle Science Editor
Tuesday, March 17, 1998
American and Russian scientists, seeking clues to possible life on one of Jupiter's major moons, have found an astonishing array of living organisms in layers of Antarctic ice hundreds of thousands of years old.
The search for new evidence of how extremely hardy Earth life can be has been spurred by recent dramatic images of the Jovian moon Europa. Deep cracks, ridges and gaps in Europa's icy surface have revealed slush and icebergs that apparently float on seas of water.
To assess whether the slush or water might hold life, researchers have been exploring deep Antarctic ice cores more than 100,000 years old -- and have detected a variety of bacteria, algae, fungus spores and other one-celled plants called diatoms.
This week, two of the scientists, astronomer Richard Hoover and his research partner Sabit S. Abyzov of the Russian Institute of Microbiology in Moscow, are working at NASA's Jet Propulsion Laboratory in Pasadena to analyze samples from the ice cores, which were retrieved by the Russians after drilling nearly a mile deep at their Vostok research station in Antarctica.
The frozen organisms may have been carried to Earth inside ancient comets, the scientists believe.
Hoover, an expert on diatoms, is from NASA's Marshall Space Flight Center in Huntsville, Ala., the place where Abyzov recently brought samples of the deep Vostok ice cores. There, he and Hoover examined them with the center's highly specialized Environmental Scanning Electron Microscope.
This instrument uses X-rays to scan samples, but unlike more conventional versions of such microscopes, the samples do not need to be coated with gold to reflect the X-rays. Thus, signs of life in the material are not hidden by the gold coating, Hoover said.
"We've seen some really bizarre things that we've never seen before," Hoover said.
At the Jet Propulsion Laboratory, meanwhile, Hoover and Abyzov are enlisting the help of microbiologist Kenneth Nealson in an effort to identify the species of the microscopic organisms they have seen. Nealson is part of the laboratory's new astrobiology division, where scientists are studying the evolution of planets and life both within and beyond the solar system.
When the first images of Europa were transmitted to Earth last year from the Galileo spacecraft that is now orbiting Jupiter and its major moons, the pictures showed clear evidence that what was once thought to be a solidly frozen ice crust covering the planet's entire surface is actually warmed in part by some interior heat source.
That discovery, in turn, aroused fervent speculation about the possibility of life.
"The combination of interior heat, liquid water and infall of organic material from comets and meteorites means that Europa has the key ingredients for life," declared Brown University geologist James Head, a member of the Galileo team when the latest images from Europa were released earlier this month.
Hoover goes even further, noting in an interview that some of the clearest images of Europa's icy regions show colored material. Some spots on the slush, he said, seem to be reddish, some bear a green tint and some are golden brown.
"I get excited in Antarctica when I see golden brown ice," Hoover said, "because to me golden brown means diatoms, and that's what shows up in the ice cores from Vostok, too. It's a safe guess that colors like that could come from biology anywhere."
Even deeper core samples from the Vostok station are still stored in a laboratory freezer in St. Petersburg, and later this month Hoover and Abyzov will bring them back to Hoover's laboratory for analysis.
The stored samples, the deepest of all the Antarctic cores, came from a drilling venture that was deliberately stopped at 3,610 meters -- more than two miles down, where the ice layer is 400,000 years old.
The reason for the halt was a dramatic one: The spot was almost exactly 100 meters above the surface of a 155-mile-long warm water lake that Soviet radar showed to be directly beneath their research station.
Russian and American scientists do not want to risk contaminating the lake with coring equipment because they eventually hope to seek evidence of life in the lake itself.
As a result, the National Aeronautics and Space Administration, together with Russian researchers, is planning ways to design a completely sterile robotic life-detecting instrument that can reach the lake and emerge with uncontaminated water samples. The device has already been named a "Cryobot," and teams from both nations will be meeting in San Diego this summer to discuss strategies for building it.
"That lake is one of the most precious resources on Earth," Hoover said. "It's the best analogue of Europa we have, and when we hunt for life down there, we'll have to be as careful about contamination as we would be when we bring back samples from the planets." Get a printer-friendly version of this article
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