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Be Well.
David
Does the Allen Hills Meteorite from Mars
Contain Fossilized Microbial Life?
© 2009 by Linda Moulton Howe
“The Allen Hills Martian meteorite suggests there is evidence
for life on ancient Mars. If that is true ... there could still be life –
particularly in the subsurface regions of Mars”
- Kathie Thomas-Keptra, Ph.D., NASA Johnson Space Center
Mars by Hubble Space Telescope, June 30, 1999.
The Allan Hills meteorite (ALH84001) that crashed into Antarctica
about 13,000 years ago. Scientists say gases in the meteorite definitely match
1976 Viking data about the Martian atmosphere. Allen Hills has magnetite
crystals in its carbonate that match similar crystals produced by Earth
bacteria. Photograph © 2000 by David J. Phillip, AP.
Three darker carbon, tiny, worm-like structures might be fossilized Martian bacteria
photographed in the Allan Hills meteorite by Kathie Thomas-Keprta at the NASA Johnson
Space Center, Houston, Texas. Small magnetite crystals were discovered inside
the worm-like structures. Photomicrograph provided by the NASA
Johnson Space Center, Houston, Texas.
Transmission electron microscopy of hexagonal-shaped magnetite
crystals (arrows) found inside the carbon worm-like structures in the Allan Hills
meteorite from Mars that might be fossilized bacteria. Image photographed by
Kathie Thomas-Keprta at the NASA Johnson Space Center, Houston, Texas.
December 24, 2009 Houston, Texas - On December 27, 1984, a team of U.S. meteorite hunters were searching in Allan Hills, Antarctica, when they discovered a 1.93 kilogram (about 4 pounds) meteorite dubbed “ALH 84001.” The rock is 3.9 billion years old and an analysis of trapped gases within ALH 84001 was an identical match to the Martian atmosphere that the 1976 Viking landers analyzed. So a new category of meteorites from Mars was confirmed.
Twelve years later after its discovery, the Allen Hills meteorite made worldwide headlines in 1996 when scientists announced the rock might contain microscopic fossils of Martian bacteria. At the time, Kathie Thomas-Keprta, a biochemist and senior scientist at Lockheed Martin's Johnson Space Center in Houston, had been studying the crystal structure and purity of magnetite beads manufactured in a species of Earth-based bacteria called magnetotactic, or MV-1. The crystals work like tiny compasses sensitive to the Earth's magnetic field. When terrestrial inorganic magnetites are studied, none have all the properties displayed in Earth's magnetotactic bacteria.
[ Editor's Note: Wikipedia - Magnetotactic bacteria (or MTB) are a class of bacteria discovered in the 1960s, that exhibit the ability to orient themselves along the magnetic field lines of Earth's magnetic field. To perform this task, these bacteria have organelles called magnetosomes that contain magnetic crystals. The biological phenomenon of microorganisms tending to move in response to the environment's magnetic characteristics is known as magnetotaxis, an instance of magnetoception. It is believed to aid these organisms in reaching regions of optimal oxygen concentration.]
Dr. Keprta then compared the Earth magnetotactic bacteria's magnetite with nearly identical magnetite crystals found in the Allan Hills meteorite from Mars. In 2000, she reported, “These populations are identical to each other. And if this Allan Hills rock were a terrestrial rock, there would be no doubt about biogenic activity associated with it. But because it comes from Mars, I'm going to have a lot of doubters!”
Doubters came forward with the hypothesis that the magnetite crystals could have resulted from thermal decomposition of the carbonate from the meteorite's impact heating.
Now nine years later and the recent development of high resolution electron microscopy, new analyses shows that at least 25% of the magnetite crystals embedded in the Allan Hills meteorite are chemically consistent with being formed by bacteria. Dr. Keprta and her NASA colleagues announced, “We feel vindicated about our original position that these structures are formed by bacteria on Mars.”
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