Science notebook--News from Antarctica and beyond

Researchers endure record temperatures

Temperatures in July at Amundsen-Scott South Pole Station were the coldest ever recorded since records began being kept in January 1957. The average monthly temperature at the station was -66.0°C (-86.8°F), breaking the old record of -64.3°C (-83.7°F) set in July 1965. The lowest temperature during the month, -77.9°C (-108.2°F) recorded on 29 July, broke a previous record for the date set in 1979.

"These very cold days provide the best conditions for astronomical observations--clear skies and low wind," commented South Pole meteorologist Matt Wolf, one of 28 people spending the winter at the research station. "On the downside," Wolf added, "power usage is at a maximum and vehicle operation is almost impossible." Amundsen-Scott South Pole Station, run year round by the National Science Foundation, supports ongoing studies in astronomy, astrophysics, atmospheric sciences, and other disciplines.

Temperatures in August followed suit. Although the monthly average did not break a record, two record daily lows were reached. On 30 August, the temperature dipped to -76.1°C (-105.0°F), breaking the previous record for the date of -72.0°C (-97.6°F) set in 1995, and on 31 August, the low of -76.4°C (-105.5°F) broke the old record for the date of -73.9°C (-101.0°F) also set in 1995.

Life in Extreme Environments award initiative examines the limits of life on Earth--and elsewhere

Scientists have found microbial life in some of the most unlikely places on Earth--in hyper-arid deserts, deep in the Earth's crust thousands of meters below the surface, entombed in ice sheets at the poles, in the bone-crushing, deep-ocean pressure of the Japan Trench, and even in human-engineered environments such as those created for industrial processes. To explore what life forms from these extreme habitats might tell us about the history of life on Earth as well as the possibility of life beyond our planet, the National Science Foundation (NSF) has launched a $6 million research initiative, Life in Extreme Environments (LExEn), involving more than 20 research projects and 40 scientists.

This Beacon sandstone from the McMurdo Dry Valleys gives evidence to the presence of life in extreme environments. The blue bands are layers of algae, fungi, and bacteria know as cryptoendolithic organisms, or organisms that live just below the surfaces of rocks. Photo courtesy of E. Imre Friedmann.

"Life flourishes on Earth in an incredibily wide range of environments," explains Mike Purdy, coordinator of the NSF award initiative. "These environments may be analogous to the harsh conditions that exist now, or have existed, on Earth and other planets. The study of microbial life forms and the extreme environments they inhabit can provide new insights into how these organisms adapted to diverse environments and can shed light on the limits within which life can exist."

One contingent of the LExEn awards will focus on microbial life in Antarctica. Four studies will examine the relationship between microbes and the harsh south polar environment.

"Protistan biodiversity in antarctic marine ecosystems: Molecular biological and traditional approaches." David A. Caron from Woods Hole Oceanographic Institute in Massachusetts will identify algae and protozoa in the sea ice, sediment, and ocean environments of the Ross Sea.
"Microbial life within the extreme environment posed by a permanent antarctic lake." Christian H. Fritsen from Montana State University will examine the survival mechanisms of viable microbial cells found in sediment aggregates in the permanent ice covers on the lakes of the McMurdo Dry Valleys.
"Longevity and diversity of microorganisms entrapped in tropical and polar ice cores." John N. Reeve from Ohio State University will identify and study microorganisms found in ice cores taken from high-altitude environments in tropical latitudes, such as the Tibetan Plateau and the South American Andes, and from both polar regions.
"Biology and ecology of south pole snow microbes." Gordon T. Taylor from the State University of New York at Stony Brook will attempt to confirm signs of microbial life found recently near Amundsen-Scott South Pole Station and, if the presence of life is confirmed, will attempt to determine if it is indigenous to the interior region or if it was brought in from coastal Antarctica, where microbial life is known to exist.

All 20 LExEn projects will involve finding techniques for isolating and culturing microbes found in extreme environments, developing methods of studying these microbes in their natural habitats, and devising technologies for recovering noncontaminated samples.

Antarctic ice sheet may not be as stable as scientists once thought

On the North Island of New Zealand, scientists have uncovered a remarkable record of sea-level fluctuations in a section of ancient coastline. Researchers believe that the story written on that nearly 5-kilometer-thick rock reveals that the massive east antarctic ice sheet has melted and frozen repeatedly and--on a geologic time frame--rapidly during its history. Further, researchers reason, New Zealand's coastline could not have been the only one to experience dramatic changes; other coastlines of the world must have varied as well.

Scientists once considered the antarctic ice sheet to be one of the most stable features on the Earth's surface. During the last decade, however, some scientists have begun to question that stability, pointing to new research that suggests that the ice sheet diminished greatly sometime in the last several million years. Understanding just how stable the ice sheet has been over history will help scientists predict how global warming might affect sea levels in the future. Should the ice in Antarctica melt completely--an unlikely scenario--the world's oceans would rise 60 meters, the height of a 12-story building.

Gary Wilson, a postdoctoral fellow at the Byrd Polar Research Center at Ohio State University, believes that the New Zealand find points to a volatile, rather than a stable, history for the east antarctic ice sheet. "The most striking thing about this record is the variability it shows," Wilson said. "There are more than 30 rises and falls of global sea level--changes of as much as 65 feet--between 2 and 6 million years ago." Wilson believes that these changes can be attributed to growing and shrinking of the antarctic ice cover. Large-scale changes, during which the mass of the current ice sheet diminishes or increases by half, occur about every 3 million years, according to Wilson's theory, and small-scale changes, reductions and increases of about a quarter of the current mass of the ice sheet, could be occurring, he believes, as often as every 300,000 years.

Fossil crayfish finds suggest earlier date, warmer clime for the origin of this species

In an ancient glacial lake bed on Mount Butters, John Isbell, a geologist from the University of Wisconsin at Milwaukee, made an unexpected find: a fossilized crayfish claw far older than any other ever found. Until now, scientists believed that crayfish first appeared about 220 million years ago, during the Mesozoic Era. Isbell's find pushes that date back 65 million years to the Carboniferous-Permian boundary, late in the Paleozoic Era. "For the first time, we now have fossils of freshwater decapod (10-legged) crustaceans that date back to the Paleozoic Era," commented Loren Babcock, associate professor of geological sciences at Ohio State University, who first determined that the fossil was the end of a crayfish's fixed finger, the stationary part of the claw. "The presence of crayfish in deposits this old," Babcock explained, "tells us that there probably were very complex freshwater ecosystems thriving by the end of the Paleozoic."

Babcock estimates that the crayfish from which the claw came was 15 to 30 centimeters long. Then as now, crayfish served both as a vehicle for cycling nutrients through freshwater ecosystems and as a primary food source for other animals. The fossil claw, Babcock speculates, was probably what was left from a predator's meal.

Another find, this one by Vanderbilt University geologist Molly Miller and Ohio State University professor emeritus of geological sciences Jim Collinson, not only supports the early development of crayfish indicated by Isbell's find, but also indicates that when the species first appeared, Antarctica was far warmer than it is now. Miller and Collinson found intricate networks of ancient crayfish burrows in deposits of rock along Kitching Ridge, about 37 kilometers from Isbell's find on Mount Butters. Some of the burrows are over 100 centimeters long and up to 15 centimeters in diameter, and they strongly resemble the burrows of modern crayfish digging in warm stream banks. "Crayfish have a very narrow temperature range within which they have to live," Babcock pointed out. "They usually must have free running water that is between 10°C and 20°C (50°F and 68°F) for at least three months out of the year. So if they were there, the climate had to be at least that warm." If Antarctica were that warm, Babcock extrapolated, "I don't know what that means for total world temperature, but my impression is that it would be pretty warm."

Famous Martian meteorite to be studied in greater depth

After headlines around the world announced that a meteorite found in the Allan Hills region of Antarctica might hold fossilized evidence of microbial life on Mars, both the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA) called for further research. Working together, the two agencies have launched an interdisciplinary program and funded studies (19 by NASA, 7 by NSF) to investigate possible traces of ancient Martian life in the meteorite, designated ALH84001 by the researchers who found it in 1984.

Some research will analyze ALH84001 itself; other studies will focus on terrestrial regions that have features similar to those of ancient Mars, such as hot springs and other extreme habitats of Earth microbes, to provide a better context for understanding the structure of ALH84001. The new research will include

scanning for extremely fine-scale alteration of the mineral interface by microbes;
analyzing oxygen and carbon isotopes to determine if they reflect a ratio typical of microbial life;
developing a chemical method to find signs of biological activity in meteorites;
examining mineral particles--oxides and sulfides of iron--which have potential as biomarkers (signs of past life);
describing the type of carbonate and associated minerals found in ALH84001 and determining the conditions and mechanisms that formed these minerals;
understanding the sources and possible biogenicity of carbon in ALH84001; and
delineating the rock's temperature history and its past infiltration by fluids.

Robot tests complete--Ready for missions to Antarctica, the Moon, and Mars

Weighing in at 720 kilograms, a four-wheeled robot named Nomad successfully completed 45 days of testing during June and July 1997 in Chile's barren, cold, and rugged Atacama Desert, paving the way for its use in Antarctica and on space missions to other worlds. During its testing, Nomad, which is about the size of a small car, traveled farther than any remotely controlled robot ever had, logging in 215 kilometers over extremely rough, high-elevation terrain, and proved its capability to respond to commands, gather samples, and send back color stereo video with human-eye resolution. Though usually controlled by scientists more than 8,700 kilometers away, Nomad often worked on its own, putting to use its four-wheel drive, four-wheel steering, and expandable chassis to avoid obstacles. It recognized meteorites planted in the desert by testers and retrieved them, and it may even have found a fossil.

"During different phases of testing," said Dave Lavery, telerobotics program manager at the National Aeronautics and Space Administration, which funded the development of the robot by Carnegie-Mellon University in Pittsburgh, "we configured the robot to simulate wide-area exploration of the Moon, the search for past life on Mars, and for the gathering of meteorite samples in the Antarctic. Nomad met or exceeded all of our objectives for this project."

Nomad's successor will join its human counterparts to search for meteorites in Antarctica during 1998 and 1999, but so far it has not been scheduled for any upcoming space missions.