[meteorite-list] Scientists Find Evidence Of Ancient Microbial Life On Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:12 2004
Message-ID: <200102262312.PAA22225_at_zagami.jpl.nasa.gov>

Kathleen Burton
Feb. 26, 2001
Ames Research Center, Moffett Field, CA
(Phone: 650/604-1371)
kburton_at_mail.arc.nasa.gov

RELEASE: 01-11AR
SCIENTISTS FIND EVIDENCE OF ANCIENT MICROBIAL LIFE ON MARS

An international team of researchers has discovered compelling
evidence that the magnetite crystals in the martian meteorite
ALH84001 are of biological origin.

The researchers found that the magnetite crystals embedded in the
meteorite are arranged in long chains, which they say could have been
formed only by once-living organisms. Their results are reported in
the Feb. 27 Proceedings of the National Academy of Sciences.

"The chains we discovered are of biological origin," said Dr. Imre
Friedmann, an NRC senior research fellow at NASA's Ames Research
Center in California's Silicon Valley and leader of the research
team. "Such a chain of magnets outside an organism would immediately
collapse into a clump due to magnetic forces," he said.

The chains were formed inside organic material whose structure held
the crystals together. "The end result looks somewhat like a string
of pearls," Friedmann noted. Each magnetite crystal in the chain is a
tiny magnet, approximately one-millionth of an inch in diameter.
Magnetite is an iron oxide, similar to iron rust.

The chains may have served as 'compasses' for the host magnetotactic
bacteria, so named because they navigate with the help of the
magnetic crystal chains inside their bodies. The chains were
preserved in the meteorite long after the bacteria themselves decayed.

The researchers say the magnetite chains probably were flushed into
microscopic cracks inside the martian rock after it was shattered by
an asteroid impact approximately 3.9 billion years ago. This
cataclysmic event on Mars' surface also may have killed the bacteria.
The same, or a later, asteroid impact ejected the rock, now a
meteorite, into space.

Another NASA research group, led by Kathie Thomas-Keprta of NASA's
Johnson Space Center, report in the same issue of PNAS that the
magnetite crystals inside the meteorite are similar to those formed
by 'modern' magnetotactic bacteria now living on Earth. The team
studied only single crystals, however, not the elusive chain-like
structures.

Friedmann's team discovered the crystal chains using a technique that
enabled them to 'see' the tiny chains inside the meteorite without
destroying them. Besides the chain-like formation, the team
discovered that individual crystals are of similar size and shape, do
not touch each other and that the chains themselves are flexible,
further evidence of biological origin.

"Until now, studying life has been like trying to draw a curve using
only one data point -- life on Earth," said Friedmann. "Now we have
two data points to draw life's curve." The next step is to find the
remains of the bacteria themselves, he said.

The fact that a small (about 4-pound) meteorite from a planet
contains large numbers of bacteria suggests that such bacteria were
widespread on the surface of Mars, the researchers say. A stone of
similar size from Earth would contain many bacteria.

In addition, since magnetotactic bacteria require low levels of
oxygen, this finding indicates that photosynthetic organisms, the
source of oxygen in the atmosphere, must have been present and active
on Mars 3.9 billion years ago.

"Finding evidence of life on Mars is one of the central problems in
astrobiology research today," said Dr. Michael Meyer, head of NASA's
astrobiology program, which funded the research.

In addition to his fellowship at NASA Ames, Friedmann, who is best
known for discovering microorganisms living inside desert rocks, is
professor emeritus of biological science at Florida State University.
Members of the research team include Dr. Jacek Wierzchos (University
of Lleida, Spain), Dr. Carmen Ascaso (CSIC, Madrid, Spain), and Dr.
Michael Winkelhofer (University of Munich, Germany).

The meteorite ALH84001 was found in the Allen Hills region of
Antarctica in 1984 by researchers supported by the National Science
Foundation's Antarctic Search for Meteorites Program, a joint effort
by the NSF, the Smithsonian Instituttion and NASA. The Case Western
Reserve University in Cleveland manages the program.

Full text of the research paper is available at:

http://www.pnas.org

Images of the magnetite chains inside the ALH84001 meteorite and, for
comparison, inside a modern magnetotactic bacterium are at:

http://amesnews.arc.nasa.gov/releases/2001/01images/magneticbacteria/bacteria.html

Ames Research Center is NASA's lead center for astrobiology, the
study of the origin, evolution, dissemination and future of life in
the universe. NASA Ames is the location of the central offices of the
NASA Astrobiology Institute, an international research consortium.

-- end --
Received on Mon 26 Feb 2001 06:12:07 PM PST