[meteorite-list] Meteor Impact Trapped Ancient Swamp Plants in Glass

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 11 Nov 2013 11:56:34 -0800 (PST)
Message-ID: <201311111956.rABJuYLm006097_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/article/dn24560-meteor-impact-trapped-ancient-swamp-plants-in-glass.html

Meteor impact trapped ancient swamp plants in glass
By Lisa Grossman
New Scientist
November 11, 2013
         
Remnants of an ancient swamp have been found preserved inside glass created
during a meteorite strike. The discovery marks the first time that traces
of life have been found to survive the heat and pressure of an impact,
adding weight to arguments that microbes travelling on space rocks could
have seeded the solar system.

Astrobiologists have long suggested that simple life forms could have
hitched a ride to Earth inside meteors, or that impacts on early Earth
could have sent terrestrial microbes to other worlds on ejected pieces
of our planet. We know that rocks kicked up by impacts can travel vast
distances. Martian meteorites with soil trapped inside have landed on
Earth, and theoretical calculations suggest that meteor strikes on Earth
could have had enough energy to send rocks as far away as the moons of
Jupiter and Saturn.

But this concept, called panspermia, also assumes that the organic compounds
essential to life as we know it can survive the extreme pressures and
temperatures of a crash-landing. Now, evidence has been found around Darwin
crater in Tasmania, which was formed by an impact about 800,000 years
ago.

Swamp life

Glass created when rock melted during the impact is strewn in a
400-square-kilometre field around the crater. Kieren Torres Howard was
conducting doctoral research at the University of Tasmania in Hobart,
Australia, studying the distribution and composition of the impact glass.
Taking a closer look with an X-ray diffraction machine, he found that the
glass is unexpectedly shot through with tiny spherical inclusions. The
glass is also riddled with geometrically regular pockets, like a honeycomb.

Howard and colleagues ground up the glass and sorted through the fragments
with an acupuncture needle to pick out the inclusions, the largest of
which was about 200 micrometres across. Chemical analysis showed that
the inclusions were rich in organic material similar to that in a peat
swamp, including cellulose and polymers that might derive from leaf cuticles.

"They looked really pristine," says Howard, who is now at the City University
of New York in Brooklyn. "It's not just that you see a signature of organic
materials, it's almost as if you took the signature of a swamp today."
Previous evidence found at the crater site, including a species of burrowing
crayfish that has probably lived in the area for the past million years,
had suggested that the region was a swamp or rainforest when Darwin crater
was formed.

"That's what allowed us to really believe we'd found some organics. We
knew this was a swamp impact," says Howard. The team think that a meteor
smacked into the ground and melted some of the upper rock to form the
impact glass. Bits of plant matter found its way into the molten glass
as everything was hurled away by the impact. The water and other volatile
compounds in the plants immediately boiled, making a bubbling froth that
froze inside the glass as it cooled, creating the honeycomb of pockets.

Funky implications

"I think it is well argued, and they made a very interesting discovery,"
says Christian Koeberl of the Natural History Museum in Vienna, Austria,
who was not involved in the new work. "It is the first time to my knowledge
that organic material has been found preserved in such a way within impact
glass."

So could pieces of an ancient swamp on Earth have gone flying off into
space? It's plausible, the team says, and organics trapped inside glass
would be somewhat protected from cosmic radiation on an interplanetary
journey. "That's when the implications get much more funky," says Howard.
"There's not much challenge in dispersing this stuff. Some material might
end up on the moon, some might end up on Mars. The material would be ejected
into space in a well-preserved state."

NASA's Curiosity rover may have already found Martian impact glass at
its home in the Red Planet's Gale crater, according to a presentation
at the Geological Society of America meeting in Colorado last month. Curiosity
doesn't have the dexterity to pick up these shards and run analyses on
them, says John Mustard of Brown University in Providence, Rhode Island.
But such glasses could be good targets for future sample-return missions
aiming to bring Mars rocks back to Earth. Scientists here could then run
tests to see if terrestrial material has landed on Mars, or if the glass
contains preserved traces of long-lost Martian vegetation.

"Could it have been the mechanism by which panspermia happened? Sure,"
says Mustard. "It allows the packaging and interplanetary transfer of
organic material."

Journal reference: Nature Geosciences, DOI: 10.1038/ngeo1996
Received on Mon 11 Nov 2013 02:56:34 PM PST