UC Berkeley scientist urges drilling into frozen lake under ice near South Pole as prelude to drilling into subglacial lakes in Antarctica and on Mars
Measurements of the ice temperature far below the
South Pole suggest that a so-called “lake” discovered at the base of
the ice is most likely permafrost – a frozen mixture of dirt and ice
– because the temperature is too low for liquid water.
Far from being a disappointment, says a University of
California, Berkeley physicist, the permafrost subglacial lake may be
ideal for developing and testing sterile drilling techniques needed
before scientists attempt to punch through the ice into pristine
liquid lakes elsewhere in Antarctica in search of exotic microbes.
Techniques that avoid contaminating a drill site with
microbes also would prove useful for future drilling into Mars’ polar
caps in search of life.
“This would be an excellent place to develop a sterile
drill,” said P. Buford Price, professor of physics at UC Berkeley and
one of more than 100 collaborators in the Antarctic Muon and Neutrino
Detector Array (AMANDA) observatory project. “Then, if we find that
we’ve inadvertently contaminated the permafrost lake, we can be
confident that the contamination is confined to only a small area.*t3P>
Drilling into a frozen lake 2.8 kilometers below South Pole
Station would have scientific interest in its own right, he said.
“We are likely to find interesting microbial life in the
permafrost, in addition to learning how to drill in a sterile way,”
he said.
Price, a cosmic ray physicist, and colleagues in the United
States and Russia made the recommendation in a paper that appeared in
the June 11 issue of the Proceedings of the National Academy of
Sciences. In their paper, the team reported data on temperature
versus depth down to 2.3 kilometers beneath South Pole Station, based
on temperature sensors implanted as part of the AMANDA project.
AMANDA is a National Science Foundation-funded array of
detectors imbedded in deep ice at the South Pole and primed to look
for high-energy neutrinos originating in exotic objects outside our
solar system, such as black holes or the active centers of distant
galaxies. AMANDA will become part of a larger, kilometer-scale
neutrino observatory named IceCube, for which funding by NSF began
earlier this year.
Based on measurements down to 2.3 kilometers, the team
estimated the temperature at the bottom of the ice, 2.8 kilometers
below the surface. This temperature – 9 degrees below zero Celsius
(about 15 degrees Fahrenheit) – is 7 degrees colder than the
temperature at which ice melts under the pressure of nearly 3
kilometers of ice.
Several years ago, radar images of the ice around the South
Pole showed evidence of a subglacial lake about 10 kilometers from
the pole. Price said that the temperature there should be about the
same as the temperature at the AMANDA site, meaning that the
under-ice lake would likely be a frozen mixture of ice and sediment
in order to explain the flat terrain indicated by radar images. The
permafrost, similar to that found in Arctic regions of North America
and Europe, may be 10 or 20 million years old, dating from before the
Antarctic continent was covered by a sheet of ice.
Since any contamination introduced by drilling into the
permafrost would not travel far, the site would make a good place to
test such techniques in preparation for drilling into Lake Vostok, a
huge, Lake Ontario-sized subglacial sea that has intrigued scientists
since it was detected four kilometers below the ice in 1996.
Proposals to drill into Lake Vostok have met with opposition
because of the danger of contamination. In addition, many of the
nearly 100 under-ice seas discovered to date may be interconnected,
so contaminating one could contaminate them all. An international
committee is discussing the issue, which may delay drilling for a
decade.
Drilling first at the site near the South Pole also would be
more convenient, because there currently are no permanent facilities
near Antarctica’s subglacial lakes comparable to South Pole Station.
As part of the AMANDA and IceCube projects, temperature
gauges were installed in bore holes that had been drilled with hot
water down to 2,345 meters, nearly to the base of the ice at 2,810
meters at the South Pole. The gauges provided a detailed profile of
temperature under the surface and also allowed Price and his
colleagues to predict the temperature at the base of the ice: -9°C
Price is primarily interested in the kinds of exotic microbes
that might live inside solid ice, either as dormant spores or at a
low level of activity. He said that life has been found wherever
people have looked, from deep in the Earth’s crust to high-altitude
clouds, and he thinks they also reside deep inside glacial ice. In
fact, he will present a poster on life in solid ice at the
Bioastronomy 2002 meeting in Australia during the week of July 8.
Such creatures would not live in ice crystals, but in
interconnected liquid veins at the boundaries where ice crystals meet.
“Even at temperatures far below the freezing point, there is
always some liquid,” he said. “As water freezes, soluble salts and
acids are excluded from the interiors of the freezing crystals,
creating a network of thin liquid veins rich in nutrients for energy
and elements such as carbon necessary for building more microbes.
Bacteria are small enough to fit and move inside the veins. Why
wouldn’t bacteria take advantage of that? Well, they probably do.”
He and UC Berkeley colleagues have developed instruments that
they have lowered into boreholes in Greenland and Antarctic ice to
search for microbial life. The devices flash ultraviolet light, and
detectors record any telltale fluorescence from bacteria. Such
fluorescence is faint, however, and the team is still perfecting the
instrument.
In a second approach, Price and his colleagues have built at
UC Berkeley a refrigerated box in which they can investigate sections
of ice cores from Antarctica and Greenland in search of exotic,
deep-ice bacteria new to science. With a fluorescence microscope
mounted inside the cold box, they can search for the faint light
emitted by fluorescing bacteria.
“With the refrigerated microscope, we can catch any microbes
trapped in liquid veins in their icy habitats,” Price said. “This
greatly reduces the possibility of contamination. If we just looked
in melted ice, we wouldn’t know where the bacteria had come from.”
Price laid out his reasons for looking in frozen ice for
unusual microbes in a paper in the February 1, 2000, issue of PNAS.
He argued that ice-loving bacteria, or psychrophiles, could easily
live in interconnecting veins of liquid water formed where three ice
crystals intersect. Such microbes could survive for hundreds of
thousands of years at a temperature just below freezing, metabolizing
but probably not multiplying. They would have to endure darkness, 400
times the pressure at the surface, no oxygen, a starvation diet and
probably a highly acidic or salty environment.
He estimated that colder ice as old as 400,000 years could
still support one cell per cubic centimeter.
Drilling in Antarctic ice, including to within about 100
meters of Lake Vostok, has turned up some bacteria, according to
Russian scientists, but all were known before. Bacteria also have
been found in ocean ice. Price and other scientists hope to discover
new species in solid ice, analogous to the novel thermophiles found
in hot seafloor vents living at temperatures above the sea-level
boiling point of water (100°C or 212°F).
All this makes it essential that drills not introduce
bacteria into a new environment, whether a sub-glacial lake isolated
for half a million years or the ice caps of Mars. No sterile drilling
has ever been achieved, Price said, though some drilling under
“aseptic” conditions has been claimed. Even the sterilization
procedure taken before sending the Voyager spacecraft to Mars were,
in retrospect, insufficient to kill many microbes discovered in t”>0D
intervening 25 years.
“If microbes can exist in glacial ice on Earth, they can also
exist in Martian permafrost and in certain regions of Jupiter’s
ice-covered moons,” he said.
Price’s colleagues on the recent PNAS paper are Oleg V.
Nagornov of the Moscow Engineering Physics Institute; Ryan Bay,
Dmitry Chirkin, Predrag Miocinovic and Kurt Woschnagg of UC Berkeley;
Yudong He of Rosetta Inpharmatics in Kirkland, Wash.; Austin Richards
of Indigo Systems Corporation in Santa Barbara, Calif.; Bruce Koci of
the Space Sciences and Engineering Laboratory at the University of
Wisconsin, Madison; and Victor Zagorodnov of the Byrd Polar Research
Center at Ohio State University in Columbus.
###
NOTE: Buford Price can be reached until Wednesday, July 3, and after
Wednesday, July 24, at (510) 642-4982 or bprice@uclink4.berkeley.edu.
