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Study of Martian Meteorite Reveals Markings Similar to Bacteria-EtchedRocks on Earth (Forwarded)



 
 
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Old March 24th 06, 01:38 AM posted to sci.space.news
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Default Study of Martian Meteorite Reveals Markings Similar to Bacteria-EtchedRocks on Earth (Forwarded)

News and Communications
Oregon State University
Corvallis, Oregon

Media Contact:
Mark Floyd, 541-737-0788

Source:
Martin Fisk, 541-737-5208

Media Release: 03-23-06

Study of Martian Meteorite Reveals Markings Similar to Bacteria-Etched
Rocks on Earth

CORVALLIS, Ore. -- A new study of a meteorite that originated from Mars
has revealed a series of microscopic tunnels that are similar in size,
shape and distribution to tracks left on Earth rocks by feeding bacteria.

And though researchers were unable to extract DNA from the Martian rocks,
the finding nonetheless adds intrigue to the search for life beyond Earth.

Results of the study were published in the latest edition of the journal
Astrobiology.

Martin Fisk, a professor of marine geology in the College of Oceanic and
Atmospheric Sciences at Oregon State University and lead author of the
study, said the discovery of the tiny burrows do not confirm that there is
life on Mars, nor does the lack of DNA from the meteorite discount the
possibility.

"Virtually all of the tunnel marks on Earth rocks that we have examined
were the result of bacterial invasion," Fisk said. "In every instance,
we've been able to extract DNA from these Earth rocks, but we have not yet
been able to do that with the Martian samples.

"There are two possible explanations," he added. "One is that there is an
abiotic way to create those tunnels in rock on Earth, and we just haven't
found it yet. The second possibility is that the tunnels on Martian rocks
are indeed biological in nature, but the conditions are such on Mars that
the DNA was not preserved."

More than 30 meteorites that originated on Mars have been identified.
These rocks from Mars have a unique chemical signature based on the gases
trapped within. These rocks were "blasted off" the planet when Mars was
struck by asteroids or comets and eventually these Martian meteorites
crossed Earth's orbit and plummeted to the ground.

One of these is Nakhla, which landed in Egypt in 1911, and provided the
source material for Fisk's study. Scientists have dated the igneous rock
fragment from Nakhla -- which weighs about 20 pounds -- at 1.3 billion
years in age. They believe that the rock was exposed to water about 600
million years ago, based on the age of clay found inside the rocks.

"It is commonly believed that water is a necessary ingredient for life,"
Fisk said, "so if bacteria laid down the tunnels in the rock when the rock
was wet, they may have died 600 million years ago. That may explain why we
can't find DNA -- it is an organic compound that can break down."

Other authors on the paper include Olivia Mason, an OSU graduate student;
Radu Popa, of Portland State University; Michael Storrie-Lombardi, of the
Kinohi Institute in Pasadena, Calif.; and Edward Vicenci, from the
Smithsonian Institution.

Fisk and his colleagues have spent much of the past 15 years studying
microbes that can break down igneous rock and live in the obsidian-like
volcanic glass. They first identified the bacteria through their signature
tunnels then were able to extract DNA from the rock samples -- which have
been found in such diverse environments on Earth as below the ocean floor,
in deserts and on dry mountaintops.

They even found bacteria 4,000 feet below the surface in Hawaii that they
reached by drilling through solid rock.

In all of these Earth rock samples that contain tunnels, the biological
activity began at a fracture in the rock or the edge of a mineral where
the water was present. Igneous rocks are initially sterile because they
erupt at temperatures exceeding 1,000 degrees C -- and life cannot
establish itself until the rocks cool. Bacteria may be introduced into the
rock via dust or water, Fisk pointed out.

"Several types of bacteria are capable of using the chemical energy of
rocks as a food source," he said. "One group of bacteria in particular is
capable of getting all of its energy from chemicals alone, and one of the
elements they use is iron -- which typically comprises 5 to 10 percent of
volcanic rock."

Another group of OSU researchers, led by microbiologist Stephen
Giovannoni, has collected rocks from the deep ocean and begun developing
cultures to see if they can replicate the rock-eating bacteria. Similar
environments usually produce similar strains of bacteria, Fisk said, with
variable factors including temperature, pH levels, salt levels, and the
presence of oxygen.

The igneous rocks from Mars are similar to many of those found on Earth,
and virtually identical to those found in a handful of environments,
including a volcanic field found in Canada.

One question the OSU researchers hope to answer is whether the bacteria
begin devouring the rock as soon as they are introduced. Such a discovery
would help them estimate when water -- and possibly life -- may have been
introduced on Mars.

About the OSU College of Oceanic and Atmospheric Sciences: COAS is
internationally recognized for its faculty, research and facilities,
including state-of-the-art computing infrastructure to support real-time
ocean/atmosphere observation and prediction. The college is a leader in
the study of the Earth as an integrated system, providing scientific
understanding to address complex environmental challenges.

IMAGE CAPTION:
[http://oregonstate.edu/dept/ncs/photos/nakhla.jpg (186KB)]
A microscopic view into a thin slice of the Martian meteor Nakhla.


 




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