[meteorite-list] NASA Study Shows Asteroids May Have Accelerated Life on Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 20 May 2009 13:35:38 -0700 (PDT)
Message-ID: <200905202035.NAA14087_at_zagami.jpl.nasa.gov>

May 20, 2009

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

Jim Scott
University of Colorado, Boulder
303-492-3114
jim.scott at colorado.edu

RELEASE: 09-111

NASA STUDY SHOWS ASTEROIDS MAY HAVE ACCELERATED LIFE ON EARTH

WASHINGTON -- A NASA-funded study indicates that an intense asteroid
bombardment nearly 4 billion years ago may not have sterilized the
early Earth as completely as previously thought. The asteroids, some
the size of Kansas, possibly even provided a boost for early life.

The study focused on a particularly cataclysmic occurrence known as
the Late Heavy Bombardment, or LHB. This event occurred approximately
3.9 billion years ago and lasted 20 to 200 million years. In a letter
published in the May 21 issue of Nature magazine titled "Microbial
Habitability of the Hadean Earth during the Late Heavy Bombardment,"
Oleg Abramov and Stephen J. Mojzsis, astrobiologists at the
University of Colorado's Department of Geological Sciences, report on
the results of a computer modeling project designed to study the
heating of Earth by the bombardment.

Results from their project show that while the Late Heavy Bombardment
might have generated enough heat to sterilize Earth's surface,
microbial life in subsurface and underwater environments almost
certainly would have survived.

"Exactly when life originated on Earth is a hotly debated topic," said
Michael H. New, the astrobiology discipline scientist and manager of
the Exobiology and Evolutionary Biology Program at NASA Headquarters
in Washington. "These findings are significant because they indicate
that if life had begun before the LHB or some time prior to 4 billion
years ago, it could have survived in limited refuges and then
expanded to fill our world."

"Our new results point to the possibility life could have emerged
about the same time that evidence for our planet's oceans first
appears," said Mojzsis, principal investigator of the project.

A growing scientific consensus is that during our solar system's
formation, planetary bodies were pummeled by debris throughout the
Late Heavy Bombardment. A visual record of the event is preserved in
the form of the scarred face of our moon. On Earth, all traces of the
bombardment appear to have been erased by rock recycling forces like
weathering, volcanoes or other conditions that cause the crust to
move or change.

Surface habitats for microbial life on early Earth would have been
destroyed repeatedly by the bombardment. However, at the same time,
impacts could have created subsurface habitats for life, such as
extensive networks of cracks or even hydrothermal vents. Any existing
microbial life on Earth could have found refuge in these habitats. If
life had not yet emerged on Earth by the time of the bombardment,
these new subsurface environments could have been the place where
terrestrial life emerged.

"Even under the most extreme conditions we imposed on our model, the
bombardment could not have sterilized Earth completely," said
Abramov, lead author of the paper. "Our results are in line with the
scientific consensus that hyperthermophilic, or 'heat-loving,'
microbes could have been the earliest life forms on Earth, or
survivors from an even more ancient biosphere. The results also
support the potential for the persistence of microbial biospheres on
other planetary bodies whose surfaces were reworked by the
bombardment, including Mars."

NASA's Astrobiology Program's Exobiology and Evolutionary Biology
Program and the NASA Astrobiology Institute at NASA's Ames Research
Center at Moffett Field, Calif., through its support of NASA's
Postdoctoral Program, provided funding for this research. The
Astrobiology Program supports research into the origin, evolution,
distribution and future of life on Earth and the potential for life
elsewhere.

For more information about NASA's astrobiology activities, visit:

http://astrobiology.nasa.gov
        
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Received on Wed 20 May 2009 04:35:38 PM PDT