Mars-Like Atacama Desert Could Explain Viking 'No Life' Results

Kathleen Burton Nov. 7, 2003
NASA Ames Research Center, Moffett Field, Calif.
Phone: 650/604-1731 or 604-9000
E-mail:

Robert Anderson
Louisiana State University, Baton Rouge, LA
Phone: 225/578-3871
E-mail:

Licenciada Guadalupe Dias
Universidad Nacional Autonoma de Mexico, Mexico City, MX
Phone: 52-55/5622-1087
Email:

RELEASE: 03-87AR
MARS-LIKE ATACAMA DESERT COULD EXPLAIN VIKING 'NO LIFE' RESULTS

A team of scientists from NASA, the Universidad Nacional Autonoma de
Mexico, Louisiana State University and several other research
organizations has discovered clues from one of Earth's driest deserts
about the limits of life on Earth, and why past missions to Mars may
have failed to detect life.

The results were published this week in Science magazine in an
article entitled "Mars-like Soils in the Atacama Desert, Chile, and
the Dry Limit of Microbial Life."

NASA's Viking missions to Mars in the 1970s showed the martian soil
to be disappointingly lifeless and depleted in organic materials, the
chemical precursors necessary for life. Last year, in the driest part
of Chile's Atacama Desert, the research team conducted
microbe-hunting experiments similar to Viking's, and no evidence of
life was found. The scientists called the finding "highly unusual" in
an environment exposed to the atmosphere.

"In the driest part of the Atacama, we found that, if Viking had
landed there instead of on Mars and done exactly the same
experiments, we would also have been shut out," said Dr. Chris McKay,
the expedition's principal investigator, who is based at NASA Ames
Research Center, Moffett Field, Calif. "The Atacama appears to be the
only place on Earth Viking would have found nothing."

During field studies, the team analyzed Atacama's depleted Mars-like
soils and found organic materials at such low levels and released at
such high temperatures that Viking would not have been able to detect
them, said McKay, who noted that the team did discover a
non-biological oxidative substance that appears to have reacted with
the organics -- results that mimicked Viking's results.

"The Atacama is the only place on Earth that I've taken soil samples
to grow microorganisms back at the lab and nothing whatsoever grew,"
said Dr. Fred A. Rainey, a co-author from Louisiana State University,
who studies microorganisms in extreme environments.

According to the researchers, the Atacama site they studied could
serve as a valuable testbed for developing instruments and
experiments that are better tailored to finding microbial life on
Mars than
the current generation. "We think Atacama's lifeless zone is a great
resource to develop portable and
self-contained instruments that are especially designed for taking
and analyzing samples of the martian soil," McKay said.

More sophisticated instruments on future sample-return Mars missions
are a necessity if scientists are to avoid contaminating future
martian samples, McKay noted. "We're still doing the first steps of
instrument development for Mars." Recently, researchers have
developed a method to extract DNA from soil without humans getting
involved in processing the data, which is "a step in the right
direction," according to McKay.

The reason Chile's Atacama Desert is so dry and virtually sterile,
researchers say, is because it is blocked from moisture on both sides
by the Andes mountains and by coastal mountains. At 3,000 feet, the
Atacama is 15 million years old and 50 times more arid than
California's Death Valley. The scientists studied the driest part of
the Atacama, an area called the 'double rain shadow.' During the past
four years, the team's sensor station has recorded only one rainfall,
which shed a paltry 1/10 of an inch of moisture. McKay hypothesizes
that it rains in the arid core of the Atacama on average of only once
every 10 years.

The Atacama research was funded by NASA's Astrobiology Science and
Technology for Exploring Planets program, by Louisiana State
University, the National Science Foundation and by several other
organizations.

The article was also authored by Dr. Rafael Navarro-Gonzalez, Dr.
Paola Molina and Dr .Jose de la Rosa from the Universidad Nacional
Autonoma de Mexico, Mexico City, MX; Danielle Bagaley, Becky Hollen
and Alanna Small, Louisiana State University, Baton Rouge, LA.; Dr.
Richard Quinn, the SETI Institute, Mountain View, Calif.; Dr. Frank
Grunthaner, NASA Jet Propulsion Laboratory, Pasadena, Calif.; Dr.
Luis Caceres, Instituto del Desierto y Departameno de Ingenieria,
Quimica; and Dr. Benito Gomez-Silva, Instituto del Desierto y unidad
de Bioquimica, Universidad de Antofagasta, Antofagasta, Chile.

For images of the field experiments, please go to:
www.sciencemag.org

-end-

In article ,
Ron Baalke wrote:
...said McKay, who noted that the team did discover a
non-biological oxidative substance that appears to have reacted with
the organics -- results that mimicked Viking's results.

I finally got around to reading that issue of Science, and found this
paper most interesting. The press release plays up the sterility of the
soil, which is indeed remarkable, and the high temperatures needed to
release what slight traces of organics are present, but it has only that
one passing allusion to what is (to my mind) the most important finding:
there is some kind of non-biological oxidant in the soil!

The exact nature of the oxidant is undetermined -- interestingly enough,
chemical tests for the obvious candidates (and the ones that have been
proposed for the Martian surface) all came up negative -- but there is
something in there that's roughly duplicating what Gil Leven's Labeled
Release experiment did on Mars. And it would appear to be non-biological,
because it doesn't care whether the glucose it chews up is right-handed
(normal for Earth life) or left-handed, whereas bacteria eat only the
right-handed glucose.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |