News: Tiny Tunnels in Mars Rock Hint at Possibility of Life

http://news.yahoo.com/s/space/20060324/sc_space/tinytunnelsinmarsrockhintatpossibilityoflife
Tiny Tunnels in Mars Rock Hint at Possibility of Life

Leonard David
Senior Space Writer
SPACE.com Thu Mar 23, 8:00 PM ET

A study of a meteorite that fell in Egypt nearly 95 years ago may
offer clues as to the search for possible life on Mars.

Researchers studying the meteorite that originated from Mars found a
series of microscopic tunnels within the object that mimic the size,
shape and distribution to tracks left on Earth rocks by the feeding
frenzy of bacteria.

The discovery of the tiny burrows adds intrigue to the search for life
beyond Earth. However, no DNA could be extracted from the meteorite,
so it's not known if the tunnels are of biological origin. The
scientists said the lack of DNA also does not derail the prospect.

Martin Fisk, a professor of marine geology in the College of Oceanic
and Atmospheric Sciences at Oregon State University (OSU) in
Corvallis, Oregon is lead author of a study team's research findings,
published in the February issue of the bimonthly journal, Astrobiology
and announced today.

Bacterial invasion

A focus of their work is the Nakhla meteorite that fell from the sky
in 1911 near Nakhla in Egypt. The object was later identified as
belonging to an exclusive group of objects known as SNC meteorites?a
subgroup of which is the nakhlites?considered to come from the surface
of Mars.

Scientists have dated the igneous rock fragment from Nakhla 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.

"Virtually all of the tunnel marks on Earth rocks that we have
examined were the result of bacterial invasion," Fisk explained in an
OSU press statement. "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."

That being the case, there are two likely scenarios.

"One is that there is an abiotic [non-living] way to create those
tunnels in rock on Earth, and we just haven't found it yet," Fisk
said. "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."

Fisk said it is commonly believed that water is an essential
ingredient for life. "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."

Handful of environments

How do scientists know that the meteorite can from the red planet in
the first place?

Nakhla is one of more than 30 meteorites identified as coming from
Mars, hurled off that planet due to asteroid or comet impacts long
ago. Eventually, after tumbling through space, a few crossed Earth's
orbit and came to full-stop on our planet.

The SNC meteorites contain gas trapped in their interiors. The
composition of this gas has been found to be nearly identical to that
of the atmosphere on the red planet, as measured by
NASA's twin Viking Mars landers in 1976.

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 in Canada.

Scientists have come across rock-eating microbes here on Earth in a
wide assortment of places?below the ocean floor, in desert settings,
and on dry mountaintops, Fisk and his colleagues point out.

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

Along with Fisk, other authors on the Astrobiology 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.

Old claim, new data

In other Mars meteorite research, an international team of scientists
will fuel more debate about the 1996 NASA-led assertion that another
Martian meteorite?Allan Hills 84001, or ALH 84001?contained tell-tale
signs of past biological activity on Mars.

The claim centered on whether organic compounds and tiny globules of
carbonate minerals imbedded in that meteorite may have been processed
by Martian biology. Indeed, the tiny carbonate globules from the
meteorite seem to resemble minerals that arise from microbial activity
on Earth.

But a fresh take on this issue will show that such carbon complexes in
ALH 84001 likely formed by non-biological processing on Mars,
according to Andrew Steele of Carnegie Institution's Geophysical
Laboratory in Washington, D.C.

The new ALH 84001 research is to be presented at NASA's Astrobiology
Science Conference (AbSciCon) 2006 being held March 26-30 in
Washington, D.C.
--
Bob.

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