LAKE HOARE, Antarctica (Mar 14, 1995) -- It has been nearly 19 years since two Viking spacecraft analyzed Martian soil and failed to find any evidence of past or present life. But some biologists believe that at least fossil remnants of extinct life may yet be found on the red planet, and that Antarctica offers clues to where future Mars explorers should look.
Almost since the time of the two Viking missions in 1976, planetary scientists have focused attention on the region of Antarctica known as the dry valleys - a network of glacial gorges and valleys transecting the Royal Society mountain range and leading to the west coast of the Ross Sea. As a result of high winds that sweep away the snow and the mountain range that obstructs the downward flow of ice from the polar plateau, the valleys are almost bare of snow and ice.
The dry valleys are as inhospitable to life as any place on this planet. From time to time a straying seal or penguin wanders inland seal and bird mummies lie scattered across the harsh gray landscape.
But despite the intense cold, dryness and lack of light during half of each year, life maintains a tenuous toehold in the Valleys. Some lichens and bacteria have colonized spaces between protective layers of sandstone, and bacteria have formed dense mats at the bottom of ice-covered lakes. Nematode worms, yeasts and even a few insects have found niches in the generally hostile ecology.
Dr. E. Imre Friedmann of Florida State University has spent 13 Antarctic summers studying the hardy but elusive organisms inhabiting the dry valleys. Now 73, he completed his latest arduous research season in the dry valleys in January. He believes that more discoveries await scientists in the region.
It could be, some scientists believe, that life at a similarly primitive level once existed on Mars - if, as they believe, Mars once had lakes.
Liquid water is not known to exist anywhere on present-day Mars. But between four billion and two billion years ago, Mars may have had lakes very much like Antarctica's Lake Hoare, Lake Vanda, Lake Bonney, Lake Fryxell and several other small ones, in the view of Dr. Robert A. Wharton Jr., of the Desert Research Institute, in Reno, Nev.
Dr. Wharton, who formerly conducted research for the National Aeronautics and Space Administration, has led a long series of research expeditions to the dry valleys and spent most of the past Antarctic summer at Lake Hoare, a four-mile-long lake in Taylor Valley.
During Mars's early history, the planet may have had a much denser atmosphere than it does now, its climate may have been warmer, and liquid water was probably prevalent, especially in the form of outflow channels discharging water from underground aquifers. Photographs of Mars show many valleys similar in appearance to terrestrial river valleys, with tributaries, meanders, deltas and other river features common on Earth. "From a biological perspective," Dr. Wharton said, "it is during this period when life could have arisen."
A system of Martian canyons some 1,500 miles long named Valles Marineris may be a particularly good place to look for the fossil remnants of primitive life, Dr. Wharton and other scientists believe. There are features in the region that look very much like the layered deposits of silt that form in lakes like those in Antarctica, and these may actually be the remains of "paleolakes" where Martian microorganisms or other simple life forms could once have lived.
"While life outside the Earth's atmosphere has yet to be observed," Dr. Wharton said, "there is a general consensus among exobiologists that the most productive search strategy for life would be based on locating liquid water."
Meanwhile, Dr. Wharton and his colleagues at Lake Hoare - Dr. Dale T. Anderson, Dr. Ian Hawes and Dr. Ann-Maree Schwarz, among others - have spent much of the past four months in diving suits, measuring and photographing the fragile life that survives some 100 feet deep in frigid water under a crust of ice 10 feet thick.
Gasping into the microphones in their face masks from the intense cold of the water, the divers have spent up to 40 minutes deeply submerged, paying out their lifelines in the dim light. While underwater, they marked growth patterns of bacterial mats, measured reproduction and metabolism rates, and brought up samples of water and microorganisms. Some of the bacterial mats they investigated are up to 100 years old, they estimate.
Life at the margins of survival - extreme heat as well as extreme cold - was explored in Antarcticain the hope of elucidating not only the defense mechanisms organisms evolve in hostile environments but the origins of life itself.
Dr. Karl Stetter of the University of Regensburg, Germany, and Dr. Hugh Morgan, a New Zealand biologist, spent part of the summer at the rim of Mt. Erebus, one of Antarctica's two active volcanoes, where they collected bacteria from steaming hot volcanic fumaroles.
"It's hard to believe," Dr. Stetter said, "but very similar species of heat-loving bacteria thrive in hot water all over the world, and we expect to find them in Antarctica. The world record for these hyperthermophyllic bacteria so far is held by a little bug called Pyrolobus fumarius, who lives near hot deep-sea vents at temperatures up to 113 degrees Celsius.
"The mystery is why the DNA and the cell membranes of these bacteria don't break down," Dr. Stetter said. "We think that vulnerable parts of the bacteria are protected by certain glycoproteins."
Paradoxically, glycoproteins in the blood of certain Antarctic fishes protect them from freezing, even when they are immersed in salty sea water at a temperature well below zero degrees Celsius (32 degrees Fahrenheit).
"It may turn out," Dr. Stetter said, "that glycoproteins have played a fundamental role in protecting primitive organisms against extremes of temperature, both hot and cold. We may be getting close to fundamental chemistry that evolved not long after the dawn of life on Earth."
Glaciologists working in the dry valley have been looking for clues to changes in the Earth's climate. Dr. Andrew G. Fountain, a glaciologist from the University of Washington, has found plenty of evidence for a disturbing pattern of change.
The glaciers in Antarctica's dry valleys, like many glaciers in other parts of the world, are melting and receding. The huge Commonwealth Glacier adjacent to Lake Vanda has been melting so fast during the past decade that the level of the lake has recently risen three feet a year Dr. Fountain said.
New Zealand's Lake Vanda research station was closed this season because of the rising water, which was about to engulf it. At Lake Hoare, Dr. Fountain's measurements of the rate of melting of the adjacent Canada Glacier and the resulting flow of meltwater into the lake showed a similar pattern.
Although scientists do not agree about whether the Earth is undergoing a long-term warming, many regard the widespread retreat of glaciers as a strongly suggestive symptom. If climatic warming should weaken and finally destroy the ice underpinnings of the West Antarctic Ice Sheet, many experts agree, the entire sheet could slide quite rapidly into the sea. This would cause an abrupt and catastrophic rise in global sea levels, flooding low-lying cities and countries like the Netherlands and Bangladesh.
Gradual, relentless planetary changes may be almost as hard to gauge on Earth as they are on Mars, but the long-term study of Antarctica's dry valleys may help scientists foresee our future a little more clearly, they hope.
Original file name: .CNI - Mars Life? 4/17
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