SETI bioastro: Fw: Antarctic Ice Seals Life's Fate

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Date: Thu Dec 19 2002 - 17:28:46 PST

----- Original Message -----
From: Ron Baalke
Sent: Thursday, December 19, 2002 2:06 PM
Subject: Antarctic Ice Seals Life's Fate

News Bureau
Office of Public Affairs
University of Illinois at Chicago
Chicago, Illinois

Paul Francuch, (312) 996-3457,

Embargoed for release until 5 p.m. EST on Monday, Dec. 16.

Antarctic Ice Seals Life's Fate

Microbes discovered packed in an ice-sealed, briny lake in
Antarctica may help advance techniques to search for signs
of life locked in the subterranean ice on Mars, and provide
a model for what lakes on Earth may have looked like during
severe glacial periods. The findings were reported in the
online edition of the Proceedings of the National Academy
of Sciences the week of Dec. 16.

A team of researchers led by Peter Doran, assistant
professor of earth and environmental sciences at the
University of Illinois at Chicago, discovered an unusual
and extreme aquatic ecosystem in Lake Vida -- among the
largest of many lakes in Antarctica's McMurdo Dry Valleys
located about 2,000 miles due south of New Zealand.

The team found a liquid lake of super-concentrated salt
water, seven times saltier than normal seawater, locked
beneath 19 meters (62 feet) of lake ice -- a record lake
ice cover on Earth. The salty water has been isolated
from the atmosphere for at least 2,800 years.

Ice core samples taken from above the pool of brine revealed
frozen bacteria and algae that came back to life after
gradual melting. The scientists believe the chilly brine
may harbor life as well.

"Any primary producers potentially living in the brine down
deep are not getting sunlight, so they would have to be
chemosynthetic, that is, getting energy from the surrounding
chemicals instead of sunlight," said Doran. "The microbes
frozen in the ice above seem to be life that was living
shallow in the lake at some time, then water flowed on top
of the thick ice cover and froze."

Carbon-14 dating showed microbes gathered from ice near the
brine to be more than 2,800 years old. Doran said the brine
is likely to be at least that old, forming as salts settled
down into it while thick ice grew outward from the sealed,
freeze-resistant salty lake.

Doran and his research team bored holes to take ice samples
from Lake Vida back in 1996 after scanning the lake with
ground penetrating radar. "It's a beautiful tool for this
because radar doesn't like salt," said Doran. "As soon as
radar sees salt, it disappears, so there's a really clear
line of where the salt begins."

With those findings, the research team mapped Lake Vida
with indications of where salt water appeared trapped.
They bored down through ice, taking core samples but
stopping in slushy water about three meters above the
brine lake. One reason for not drilling lower was fear
that special ice-melting chemicals used to help the
drilling might have contaminated samples of brine.

The research overturns earlier assumptions that Lake Vida
was frozen solid. "That's an important conclusion because
Lake Vida is in an area that has a fairly cold mean annual
temperature," said Doran. "It actually pushes back our
estimates of what it takes to freeze a lake ecosystem."

NASA is interested in the research because the Lake Vida
ecosystem serves as a classroom of sorts, providing
lessons for launching Martian ice probes that may yield
frozen microbes.

"It's pretty much common knowledge that Mars had a water-
rich past and likely went from a warmer to a colder climate,
although this last point is coming under much debate lately,"
said Doran. "Mars is very cold. It has a thin atmosphere
now and cannot support liquid water on the surface, although
there's evidence that there may be something in the near-
surface -- maybe a brine, or something like that."

"If the planet went through a cooling, Mars must have had
perennially ice-covered lakes, then this ice-sealed type of
environment," said Doran. "Unless we find evidence of life
still there today, I see Lake Vida as being like life's
last romp on Mars, potentially, in an ice-sealed lake.
Lake Vida gives us an excellent model of how long a lake
ecosystem can survive before you snuff it out by turning
down the temperature. How does the ecosystem respond, what
does it look like and, more importantly, if we go back and
collect samples, where do we look and what are we looking
for to find evidence of these types of lakes?"

NASA and the National Science Foundation are jointly funding
a follow-up study to test miniature coring equipment and to
dip a straw-like device into the brine of Lake Vida to suck-
out samples.

"We'll do it like we're on a planetary mission," said Doran.
"While we don't expect to find 'Lake Vidas' on Mars today,
it's a good analogue for something in Mars' past. Also, if
there are brines leaking out from Mars' subsurface today,
they could well come from a buried 'Lake Vida.'"

Besides Doran, the research team authors include Christian
Fritsen of the Desert Research Institute of Reno, Nev.;
Christopher McKay of the NASA Ames Research Center; and
John Priscu and Edward Adams of Montana State University.
Support for the research came from grants from the NSF and
the NASA Exobiology Program.

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