Astrobiologist to hunt small game in Siberia
Sleeping on the permafrost and drilling for ice doesn't sound like the ideal way to spend your summer.
It's remote, it's cold, and the very name carries unpleasant memories of prison camps. But it's also an ideal place to look for life-forms that have learned survival tricks that might be in use on the permafrost and polar caps of Mars, Europa, Callisto and other icy moons of the solar system.
Richard Hoover, of NASA's Marshall Space Flight Center, is headed to North Siberia for a two-month trek to hunt cryophiles, microbial extremophiles that love extreme, cold conditions like the Siberian permafrost. Already, he carries around a reminder that interesting things await: a vial of growing moss that remained alive yet dormant while frozen for 40,000 years in the permafrost of the Kolyma Lowlands of Beringia in northeastern Siberia.
It is in Kolyma that Hoover, solar physicist turned astrobiologist, will become a roughneck.
"I'll be turned into a driller's helper," Hoover explained, "after David Gilichinsky trains me. We'll be using aseptic drilling techniques to obtain deep permafrost and ice samples for microbiological research. We will examine the cores for viable and fossil diatoms, bacteria, cyanobacteria, yeast, fungi, actinomycetes and other microbial life-forms."
Gilichinsky, a member of the Institute of Soil Science and Photosynthesis of the Russian Academy of Sciences, is one of Hoover's partners in the Joint U.S./Russian Research in Space Science (JURRISS) Program. Their proposal was selected by NASA in May. In collaboration with Prof. Elena Vorobyova of Moscow State University, they proposed to conduct an in-situ study of permafrost as a microbial habitat.
Now that Siberia's brief summer is about to end, it's time for Hoover and Gilichinsky to go hunting for small game. To understand where to look, Hoover and Prof. Elena A. Vorobyova will study the microbial content of permafrost and the structure of the interface between the soil and ice.
This research is important to astrobiology for the development of techniques that could be used in exploring Mars, Europa, Callisto, Io, comets, asteroids, and other icy worlds of our solar system. Astrobiology is the study of the origin, distribution and limitations of life in the cosmos.
It seeks to answer these fundamental questions: How Does Life Begin and Develop?, Does Life Exist Elsewhere in the Universe?, and What is Life's Future on Earth and Beyond? A major element of the NASA Astrobiology Program is studying how life, in the form of microbes, survives on Earth under extreme conditions. These microbes are called extremophiles.
A cross-section of permafrost shows an ice wedge hiding just below the surface. Hoover and his Russian colleagues will hunt for wedges and pingos (see below) where microbes may be snuggled up for a very long winter's nap. The active layer is soil that will thaw in summer and refreeze in winter. Below that is permafrost - soil which is too deep for the warmth of a brief summer to reach. This sample is in the Arctic National Wildlife Refuge in northeast Alaska. U.S. Fish and Wildlife Service.
More information on ice wedges, polygons, and pingos, including an animation showing how they grow, is at the Fish & Wildlife Service site on the Arctic National Wildlife Refuge.
"The microorganisms found in the permafrost, glaciers, and polar ice caps of Earth are of profound significance to astrobiology," Hoover said. His peer-reviewed article entitled "Significance to Astrobiology of Microorganisms in Permafrost and Ice" has just been accepted for publication by Kluwer in a new book on Permafrost. It also was the topic of a paper he delivered at the SPIE Astrobiology Conference held by the Society of Photo-Optical Instrumentation Engineers in Denver on July 21, 1999.
"Dormant ancient microbes, and even higher plants such as moss, can remain viable by cryopreservation, resuming metabolic activity upon thawing after being frozen in glacial ice or permafrost for thousands to millions of years," Hoover explained. "The microbial extremophiles in the Arctic and Antarctic glaciers and permafrost represent analogs for cells that might be encountered in the permafrost or ice caps of Mars or other icy bodies of the solar system." Despite its harsh environment, Siberia is a natural resource that has been barely explored.
Hoover, Gilichinsky, and other scientists count the permafrost - soil that remains frozen year-round - to be one of those resources. Hoover said three types of life-forms are found in permafrost: active ones that eke out a living in thin water films between grains of soil and ice, viable but inactive forms that are frozen in suspended animation (deep anabiosis) until things get better, and the frozen carcasses of microbes that simply gave up and died.
"We're very excited about the living microbes and plants that we have found in permafrost and on ice wedges and glaciers and the viable but long dormant, ancient microorganisms that can be cultured from permafrost, glaciers and deep ice cores," Hoover said. " Even dead microbes from ancient permafrost and deep ice are tremendously important due to their perfect state of preservation, with intact cell membranes, organelles, proteins, DNA and RNA. They make possible an entirely new field of research that may be designated molecular paleontology."
In Siberia, Hoover is particularly interested in patterned ground ice wedges and volcano-shaped pingos.
"The ice wedges form when the ground freezes and breaks into large exposed polygonal cracks," he explained. "Water fills the cracks during warm weather, refreezes and expands the crack in the winter." The cycle repeats endlessly. Some of the permafrost ice wedges have very ancient ice at the center. This also means that any life-forms caught deep in the ice of ancient glaciers and permafrost are extremely old.
Vorobyova brought to NASA/Marshall ancient ice samples from Beacon Valley, Antarctica, and has cultured actinomycetes and bacteria from this ancient glacial ice. Studies of the Beacon Valley ice and permafrost at NASA/Marshall's Environmental Scanning Electron Microscope (ESEM) revealed the presence of large numbers of ancient bacteria, mycelial fungi and intact diatoms with extracellular polysaccharides, indicating the diatoms were still alive when frozen. Exact dating of the samples is under way, but these ancient and still viable microbes may be of Miocene age, possibly more than 8 million years old.
"I am also very interested in pingos," Hoover continued. "We have seen evidence of pingos in images of Mars from near the polar ice caps."
Pingos are soil covered ice mounds that resemble volcanoes. They are formed as ice freezes on solid permafrost between ice wedge boundaries.
"Pingos can be very big, very tall, Hoover explained, with some reaching heights of tens of meters.
"If we can find a suitable pingo, I hope to obtain samples of the interior ice. What kind of microorganisms are in there? Are there rocks that get trapped and form cryoconite holes?" Cryoconite holes can be temporary glacial micro-Edens. Cryoconite holes occur in glacial ice when dark rock on the surface of the ice get heated by sunlight and melt the ice. The water and rock dust is ideal for the growth of cyanobacteria, diatoms, bacteria, fungi, and even mosses.
"I found orange mosses covered with black films of cyanobacteria growing on the ice of the Matanuska Glacier in Alaska. Rock debris broken from mountains and rock surfaces by the moving ice and may also be captured in the ice and promote ice bubble ecosystems.
Tracking down an astrobiologist on the move
That's where [email protected] caught up with Hoover to talk with him about his trip to Siberia. The ESEM is a sophisticated tool that NASA/Marshall acquired for detailed analysis of the broken edges of failed materials. As part of his astrobiology investigation, Hoover uses it for the designer's original purpose, studying microbes without the damage that comes with most electron microscope techniques.
Hoover sat with Prof. Elena A. Vorobyova and Prof. Sabit S. Abyzov (the discoverer of deep ice microorganisms at Vostok Station, Antarctica) as they examined microscopic objects in ice from just above the surface of Lake Vostok in the Antarctic.
Hoover and Abyzov have studied Vostok ice before, but this sample is the deepest yet, 3,611 meters (2.3 miles) under the snow-swept surface and just a few dozen meters above where scientists expect to hit the liquid surface of a body as large as Lake Ontario and about 400,000 years old.
"We have reached a deep layer at 3,623 meters," Abyzov said, "and stopped because to go deeper we need the permission of an international commission for research on Lake Vostok to avoid contamination of a very ancient lake." Meanwhile, selected ice samples from just above the "lake surface" are being melted to see what traces of early life are buried with them.
"The fundamental problem is we're seeing things that we have never seen before and therefore they are very difficult to identify," Hoover said. They have found very large white filaments that are similar to filaments Hoover discovered in an ancient frozen thermokarst pond in the Cold Regions Research and Environmental Laboratory (CRREL) Permafrost Tunnel in Fox, Alaska. These white filaments may be heterotrophic cyanobacteria, which could live in total darkness by eating organic material (called heterotrophic nutrition) rather than photosynthesis.
"This is very important for studying the history of biology on our planet," Abyzov continued, "and for the future of astrobiology. We are interested in using Vostok Lake to develop methods for searching for life on Europa and Ganymede and Callisto," Jupiter's ice-covered moons.
"We really want to do a spectrum on that filament before we get away from it," Hoover interrupted. In addition to making nice pictures, the ESEM can do a chemical assay by analyzing X-rays emitted by outer electrons of atoms in the sample.
"Look at the nickel!" Hoover exclaimed a few minutes later as a mineral particle was analyzed. "We have a nice nickel peak, lots of zinc, calcium, titanium. It's a mineral. We're seeing nickel that's not inconsistent with a tiny speck of meteorite or cosmic dust."
A few microns away on the same mote, the signature changed: "It looks like you're examining a different object." And so it went as the trio explored new microterrain and developed new lessons that will help refine the search for life elsewhere in the solar system.
"Wow!," Hoover exclaimed. "That's interesting. Look at that. Elena found a beautiful Pinnularia diatom in the ancient ice from Beacon Valley."
rating: 5.00 from 1 votes | updated on: 15 May 2007 | views: 1807 |