Clues to possible life on Europa
Clues to possible life on Europa may lie buried in Antarctic ice
March 5, 1998: More than a century ago, science fiction pioneer Jules Verne wrote about people swept "Off on a Comet" and into space where they lived more or less happily ever after.
Verne's 1877 book (also published as "Hector Servadac") was a bit fanciful, but it had an element of truth: life may have hitchhiked across the solar system. The proof may be found at the ends of the Earth. This week, American and Russian scientists are examining deep ice from the Antarctic and hoping to find clues that fungi, bacteria, and even diatoms could survive conditions in icy solar system bodies. This would help make the South Pole one of the first destinations for the growing field of astrobiology.
"It's possible to say that ancient impacts of asteroids on the Earth could have ejected soil, rocks, and seawater containing terrestrial microorganisms into space, and that they may have made it to other places in the solar system," explained Richard Hoover at NASA's Marshall Space Flight Center. Hoover is an X-ray astronomer who is also is internationally known for his work on diatoms and a firm believer that living microorganisms locked in ice have a chance of remaining viable for long periods in outer space.
Click on the image at right for the location of the Vostok Station (images courtesy of USGS, Columbia University).
The debate over whether the Antarctic Allan Hills meteorites brought life from Mars (or were contaminated by life on Earth) is the best known case. Hoover said that other evidence abounds, including asteroids striking the Earth or Mars and blasting materials into space, the survival of streptococcus bacteria on the Surveyor 3 moon lander, and the survival of microorganisms inside Antarctic ice.
The possibilities expanded this week when NASA released new images and data that Europa, one of Jupiter's larger moons, slush and perhaps liquid water near the surface. That raises the intriguing possibility that Europa may harbor life.
Discoveries on the Earth over the last few years show that life thrives or can be preserved in a range of "hostile" conditions, from volcanic vents deep in ocean trenches, to ice more than 400,000 years old, to Siberian permafrost more than 5 million years old.
This week, Hoover and Dr. S. S. Abyzov of Russia's Institute of Microbiology of the Russian Academy of Sciences in Moscow are examining ancient ice drilled at Russia's Vostok (East) Station about 1,000 km (1,600 mi) from the South Pole. Eventually, they hope to examine water taken from inside a lake - liquid, not ice - discovered under Vostok Station in 1996.
The first samples being examined are from 386 meters (1,266 ft) down; the deepest in this set is from 1,249 meters (4,097 ft). Samples from as deep as 3,610 meters (11,840 ft) are on their way from Vostok to the Institute of Microbiology. Abyzov says that portions will be brought to Marshall later this year.
Russian scientists have been drilling at Vostok since 1974. In 1996, seismic and other tools revealed the lake's presence in 1996. Lake Vostok is overlaid by about 3,710 meters (12,169 ft) of ice and may be 500,000 to 1 million years old. Since the discovery, drilling has gone slowly while procedures are worked out to keep it pristine. No one has seen or sampled the lake - the deepest ice sample is from 100 meters (328 feet) above the liquid surface - nor is anyone sure why it is liquid, hence the scientific curiosity. (Check below for links to stories about Lake Vostok.)
While Lake Vostok holds clues about life on Earth, it also is a good model for conditions on Europa (the image links to the latest news from Europa). The lake is about 48 by 224 km (30 by 140 mi) in size - about the size of Lake Ontario - and 484 meters (1,600 ft) deep. Recent data indicate that it has about 50 meters (165 ft) of sediment at the bottom.
"Recent research [shows] that extremely severe conditions of cosmic environments do not exclude the possibility that microorganisms may exist in anabiotic states at high altitudes in interplanetary space," Abyzov wrote in a recent paper. The only way to resolve the question is to use the Antarctic as a model for conditions in comets, the Martian ice caps, and other icy moons orbiting Jupiter and Saturn.
At Vostok station in 1975, Abyzov discovered bacteria, fungi, diatoms, and other microorganisms which were blown to Antarctica by winds from lower latitudes. The numbers of the organisms at different depths, and thus different ages of the ice, change with major climate changes on the Earth. Thus, the ice also serves as a time capsule, preserving specimens of life as far back as 500,000 years. This offers the potential for studying how genetic material changes over the centuries.
Abyzov brought his samples to Marshall to use the Environmental Scanning Electron Microscope, or ESEM, a relatively new tool that Marshall uses to analyze how materials fail and break. It was originally designed to analyze biological specimens in their natural environment, without coating them in gold to make them reflective. And that's ideal for observing whatever is in the ice. It also uses an X-ray scan to analyze the elements in a target, an important step in determining whether an object is organic.
The ice specimens will be analyzed at Marshall over the next week, then Abyzov will go to the Jet Propulsion Laboratory to work with another colleague with different analytical tools. Check back in a few days for a follow-up story on what the ESEM finds.
Abyzov describes his research in a chapter of Antarctic Microbiology (E. Imre Friedmann, ed. ISBN: 0-471-50776-8. New York: Wiley, 1993. 644 pp.). In the book, international authorities present expert and comprehensive papers concerning the diversity of such Antarctic microorganisms as prokaryotes, fungi, algae and protozoa and their freshwater, marine and terrestrial environments. In fact, the entire ecosystem of the Antarctic continent and its surrounding seas is based primarily on microorganisms. Coverage ranges from marine sediments and sea ice to exobiological implications and environmental concerns.
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