[meteorite-list] New Evidence Strengthens Claims Of Ancient Life On Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:12 2004
Message-ID: <200102270101.RAA23706_at_zagami.jpl.nasa.gov>

February 26, 2001
Catherine E. Watson
Johnson Space Center, Houston, TX
(Phone: 281/483-5111)

Release: J01-17

NEW EVIDENCE STRENGTHENS CLAIMS OF ANCIENT LIFE ON MARS STUDY OF MARTIAN
METEORITE REVEALS MAGNETIC FOSSILS

Researchers have found magnetic material in a 4.5-billion-year-old
Martian meteorite that could only have been produced by bacteria. This
new data strongly supports the primitive life on Mars hypothesis of
David McKay and co-authors in 1996.

"There are no known reports of any organic process that could produce
such magnetites," said Kathie Thomas-Keprta, an astrobiologist at NASA's
Johnson Space Center and the lead researcher on the study. The Martian
magnetites are identical to those found in a bacteria strain on Earth
called MV-1. "This group of magnetite deeply embedded in the Mars
meteorite is so similar to the ones produced by the Earth bacteria that
they cannot be told apart by any known measurement," said David McKay, a
geologist at JSC and a co-author on the paper. "We considered that
perhaps earth bacteria or earth magnetite had gotten into the Mars
meteorite," McKay continued, "but extensive examination and testing by
both our team and many other investigators eliminated that possibility."

Scientists generally agree that ALH84001 is a member of the group of 16
meteorites found on Earth that originated on Mars. The potato-sized
igneous rock is the oldest of them – about 4.5 billion years. It lay in
Antarctic ice for more than 13,000 years. But the biogenic-type
magnetite crystals are embedded in 3.9-billion-year-old carbonates
within ALH84001. Previous work by co-author Chris Romanek, of the
Savannah River Ecology Laboratory has shown that these carbonates formed
on Mars; thus the magnetite crystals must also have formed on Mars.

Using electron microscopy, team members examined the Martian magnetites
still embedded in the carbonate and also removed about 600 crystals and
examined the individual particles to determine their chemical
composition and crystal geometry. "These crystals are so tiny, ranging
from 10 to 200 nanometers, that nearly a billion of them would fit on
the head of a pin," said Thomas-Keprta.

The authors found that about a quarter of the Martian magnetites from
ALH84001 are identical to magnetites produced on Earth by the
magnetotactic bacteria strain MV-1, which has been extensively studied
by co-author Dennis Bazylinski, a geobiologist and microbiologist at
Iowa State University who has developed many ways of culturing these
difficult to grow microorganisms. No one has found terrestrial inorganic
magnetites, produced either naturally or in the laboratory, that mimic
all the properties displayed by biogenic magnetites. "There is currently
no known inorganic chemical means of producing these magnetite crystals
with their unique morphologies," he said.

Magnetite (Fe3O4) is produced inorganically on Earth. But the magnetite
crystals produced by magnetotactic bacteria are different – they are
chemically pure and defect-free. Their size and shape is distinct.
Magnetotactic bacteria arrange these magnetite crystals in chains within
their cells. These characteristics make the magnetite crystals very
efficient compasses, which are essential to the survival behavior of the
bacteria by helping them locate sources of food and energy. "Mars is
smaller than Earth and it developed faster," co-author Simon Clemett of
Lockheed-Martin at JSC noted. "Consequently, bacteria able to produce
tiny magnets could have evolved much earlier on Mars."

"The process of evolution has driven these bacteria to make perfect
little bar magnets, which differ strikingly from anything found outside
of biology," added, Joe Kirschvink, a geobiologist at Caltech and a
co-author of the paper. "In fact, an entire industry devoted to making
small magnetic particles for magnetic tapes and computer disk drives has
tried and failed for the past 50 years to find a way to make similar
particles. A good fossil is something that is difficult to make
inorganically, and these magnetosomes are very good fossils."

Mars has long been understood to provide sources of light energy and
chemical energy sufficient to support life. Early Mars, the authors
note, may have had even more chemical energy produced by active
volcanism and hydrothermal activity. Also, when the team asserted in
1996 that Martian meteorite ALH84001 showed signs of life existing on
Mars, that planet was not known to have ever had a strong magnetic
field. But since then, the Mars Global Surveyor has observed magnetized
stripes in the crust of Mars that show a strong magnetic field existed
early in the planet’s history, about the same time as the carbonate
containing the unique magnetites was formed. Surface features also
suggest that early Mars had large oceans and lakes. These attributes,
coupled with a CO2-rich atmosphere, provided the necessary environment
for the evolution of microbes similar to the fossils found in ALH84001.

A team of 10 researchers collaborated on the four-year study, which was
published Feb. 27 in a special Astrobiology issue of the Proceedings of
the National Academy of Science. The team, led by Thomas-Keprta of
Lockheed Martin at Johnson Space Center, was funded by the NASA
Astrobiology Institute. Co-authors of the study are Simon Clemett and
Susan Wentworth of Lockheed Martin at the JSC; Dennis Bazylinski of Iowa
State University (funded by the National Science Foundation); Joseph
Kirschvink of the California Institute of Technology; David McKay,
Everett Gibson and Mary Fae McKay of JSC; and Christopher Romanek of the
Savannah River Ecology Laboratory.

For a more technical discussion of this paper please see the following
Web site:

http://ares.jsc.nasa.gov/astrobiology/biomarkers/recentnews.html

-END-
Received on Mon 26 Feb 2001 08:01:28 PM PST