[meteorite-list] New Viewing Technique Bolsters Case For Life On Mars (Nakhla Meteorite)
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Feb 9 12:29:51 2006
New Viewing Technique Bolsters Case For Life On Mars
by Staff Writers
February 8, 2006
Houston, Texas (SPX) - New examinations of a Martian meteorite found nearly a
century ago have strengthened the possibility that the red planet once harbored life.
"I don't understand the sample completely just yet, but it's exciting,"
research team member Kathie Thomas-Keprta told SpaceDaily.com.
The sample in question is from a meteorite named Nakhla, which was found
in the Egyptian desert in 1911, and which has been held since by the
Natural History Museum in London. A new examination of Nakhla has
produced a very strong indication that it might have been imbedded with
organic carbon - an absolute necessity for life - that did not originate
Keprta, a specialist in microscopy techniques and a contractor for NASA
at the Johnson Space Center, said she and colleagues recently obtained
pristine samples of the rock -which is thought to be 1.3 billion years
old - to probe its structure using the latest optical examination
"We have known for a long time about its carbon content via chemical
analysis," she explained, "but up to now no one has been able to locate it."
The team took a tiny, polished piece of the meteorite only 30
micrometers thick that was sealed in epoxy and applied a technique
called focused-ion-beam microscopy, or FIB, to carve out a small
rectangle from the sample, and another technique called transmission
electron microscopy, or TEM, to identify the deposits of carbonaceous
"For the first time, we can find the exact area" on Nakhla that harbors
the carbon," Thomas-Keprta said. Further analysis by secondary ion mass
spectroscopy, or SIMS, identified the sample as composed of carbon 13,
which she said could only have come from an extraterrestrial source, not
from any earthbound contamination.
All life on Earth contains some quantity of the isotope carbon 14, but
no carbon 13.
The deposits, which Thomas-Keprta described as "shrubby," resemble
similar structures on Earth created by the actions of ancient
microorganisms that lived within volcanic rocks on the ocean floor.
Thomas-Keprta and colleagues will present their findings next month at
the Lunar and Planetary Science Conference in Houston. The team includes
scientists who also presented evidence for microbial life in another
Martian meteorite - ALH84001, which was found in Antarctica - in 1998.
All Martian meteorites are thought to have been ejected from the red
planet's surface during ancient impacts. The meteorites drifted in
interplanetary space until captured by Earth's gravity and dragged down
to the surface.
Nakhla Paper <http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2039.pdf >
Received on Thu 09 Feb 2006 12:26:07 PM PST