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Fwd = RESEARCHERS PUBLISH LATEST RESULTS IN SEARCH FOR ANCIENT MARS LIFE

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  • Frits Westra
    Forwarded by: fwestra@hetnet.nl (Frits Westra) Originally from: NASANews@hq.nasa.gov Original Subject: RESEARCHERS PUBLISH LATEST RESULTS IN CONTINUING
    Message 1 of 1 , Aug 3, 2002
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      Forwarded by: fwestra@... (Frits Westra)
      Originally from: NASANews@...
      Original Subject: RESEARCHERS PUBLISH LATEST RESULTS IN CONTINUING SEARCH FOR ANCIENT MARTIAN LIFE
      Original Date: Fri, 2 Aug 2002 14:50:23 -0400 (EDT)

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      Dwayne Brown
      Headquarters, Washington August 2, 2002
      (Phone: 202/358-1726)

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

      RELEASE: 02-150

      RESEARCHERS PUBLISH LATEST RESULTS
      IN CONTINUING SEARCH FOR ANCIENT MARTIAN LIFE

      In the latest study of a 4.5 billion-year-old Martian
      meteorite, researchers have presented new evidence confirming
      that 25 percent of the magnetic material in the meteorite was
      produced by ancient bacteria on Mars. These latest results
      were published in the journal Applied and Environmental
      Microbiology.

      The researchers used six physical properties they refer to as
      the Magnetite Assay for Biogenicity (MAB) to compare all the
      magnetic material found in the ancient meteorite -- using the
      MAB as a biosignature. A biosignature is a physical and/or
      chemical marker of life that does not occur through random
      processes or human intervention.

      "No non-biologic magnetite population, whether produced by
      nature or in the laboratory, has ever met the MAB criteria,"
      said Kathie Thomas-Keprta, an astrobiologist at NASA's
      Johnson Space Center (JSC) in Houston and the lead researcher
      on the study. "This means that one-quarter of the magnetite
      crystals embedded in the carbonates in Martian meteorite
      ALH84001 require the intervention of biology to explain their
      presence."

      Magnetotactic bacteria, which occur in aquatic habitats on
      Earth, arrange magnetite crystals in chains within their
      cells to make compasses, which help the bacteria locate
      sources of food and energy. Magnetite (Fe3O4) is produced
      inorganically on Earth, but the magnetite crystals produced
      by magnetotactic bacteria are very different -- they are
      chemically pure and defect-free, with distinct sizes and
      shapes.

      Four of the MAB biosignature properties relate to the
      external physical structure of the magnetite crystals, while
      another refers to their internal structure and another to
      their chemical composition.

      In their earlier studies, the researchers found that
      approximately one-quarter of the nanometer-sized magnetite
      crystals in ALH84001 had remarkable physical and chemical
      similarities to magnetite particles produced by a bacteria
      strain on Earth called MV-1. This is the first time, however,
      that any researcher has used the full MAB range of
      biosignature properties to compare the proposed bacteria-
      produced crystals in Mars meteorite ALH84001with the
      bacteria-produced crystals from Earth and with the other
      magnetites in the meteorite.

      The comparison between the proposed bacteria-produced
      crystals in the meteorite and crystals known to be produced
      by Earth-bacteria MV-1 is striking and provides strong
      evidence that these crystals were made by bacteria on Mars.

      The fact that Mars Global Surveyor data suggest that early
      Mars had a magnetic field is consistent with a reason why
      Mars would have magnetotactic bacteria. "Our best working
      hypothesis is that early Mars supported the evolution of
      bacteria that share several traits with magnetotactic
      bacteria on Earth, most notably the MV-1 group," said Simon
      Clemett, a coauthor of the paper at Johnson.

      Mars has long been understood to provide the sources of light
      and chemical energy sufficient to support life, but in 2001
      the Mars Global Surveyor spacecraft observed magnetized
      stripes in the crust of Mars, which showed that a strong
      magnetic field existed in the planet's early history, about
      the same time as the carbonate containing the unique
      magnetites in ALH84001 was formed.

      In June, researchers using the Mars Odyssey spacecraft
      announced that they had found water ice under the surface of
      Mars. These attributes, coupled with a carbon dioxide-rich
      atmosphere, would have provided the necessary environment for
      the evolution of microbes similar to the fossils found in
      ALH84001.

      "We believe this latest study proves that the magnetites in
      ALH84001 can be best explained as the products of multiple
      biogenic and inorganic processes that operated on early
      Mars," Thomas-Keprta said.

      An international team of nine researchers collaborated on the
      three-year study. 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 Clemett
      and Susan Wentworth of Lockheed Martin at JSC; Dennis
      Bazylinski of Iowa State University (funded by the National
      Science Foundation); Joseph Kirschvink of the California
      Institute of Technology in Pasadena; David McKay and Everett
      Gibson of JSC; Hojatollah Vali of McGill University in
      Canada; and Christopher Romanek of the Savannah River Ecology
      Laboratory.

      For a more technical discussion of this latest publication
      please visit the following Web site:

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

      -end-

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