[meteorite-list] Martian Meteorite May Have Held Life (Nakhla Meteorite)
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Feb 10 16:02:29 2006
Martian meteorite may have held life
February 10, 2006
A mix of carbon compounds filling the miniscule veins in a Martian
meteorite has refuelled the debate on the possibility of life on Mars.
Similarities between the carbon-rich filler and that found in fractured
volcanic samples from the Earth's ocean floor dangle the possibility
that life produced the Martian material, say scientists.
A team of researchers led by David McKay and Everett Gibson of the
Johnson Space Center in Houston, US, raise the scenario as just one
possibility after extensively analysing new samples of the Nakhla meteorite.
The UK's Natural History Museum recently provided the team with fresh
samples from the interior of the meteorite, which broke into many pieces
upon landing in Egypt in 1911.
Near the tube-like veins in the rock, researchers found iddingsite - a
mineral also formed on Earth, mainly through alteration of an iron-based
mineral called olivine by water. And within the cracks, they found
carbon-rich material that appears dark brown or black.
Astrobiologists look for carbon and water in their search for
extraterrestrial life. Carbon is the building block of terrestrial life,
forming the basis for organic chemistry, and water is necessary to
support all forms of life on Earth.
Sceptics have cast doubt on previous claims of organic material in
Nakhla, saying the carbonaceous matter was simply contamination from
Earth. But Colin Pillinger, a team member from the Open University in
Milton Keynes, UK, says results from the new samples from the carefully
protected interior of the meteorite lay those concerns to rest. "We're
pretty confident this is indigenous stuff," he says. "We don't think
The work will be presented at the Lunar and Planetary Science Conference
in Houston, US, in March.
In two abstracts submitted to the conference, the team outlines possible
sources of the carbon-containing components. Either a carbon-bearing
impactor introduced them to Mars between 600,000 and 700,000 years ago
or they are "products of biogenic activity and introduced by groundwater
into the fracture features in Nakhla," the team writes.
The team cites an upcoming study by oceanographer Martin Fisk, of Oregon
State University in Corvalis, US, who compared Earth features to Martian
meteorites. The authors note "the close resemblance" of Nakhla's
carbon-rich material to carbon Fisk noted in veins within basaltic glass
from the ocean floor.
In this forthcoming paper in Astrobiology, Fisk reports that DNA is
associated with the fractures, or tunnels, in rock samples from Earth's
ocean floor, a mountain top in Oregon and a rainforest on the
California-Oregon border. "There's not DNA distributed throughout the
rock, it's very specific to the tunnels," Fisk says.
Furthermore, the size and shape of the tunnels in the Earth samples
closely resemble those seen in Nakhla. And he says researchers have yet
to see a non-biological explanation for the tunnels, although that does
not rule out the possibility.
"We're saying here's a phenomena on Earth that we're pretty darn sure
are caused by bacteria", and rocks from Mars sport similar features,
Fisk says. "I'm letting people draw their own conclusions."
Pillinger is careful to point out that the new findings do not mean the
community has definitive evidence for life on Mars. "We're finding these
very strange features, but we can't say anything more than that," he
says. "They could have come from several processes and one of them is
Received on Fri 10 Feb 2006 04:00:42 PM PST