[meteorite-list] NASA Research Shows DNA Building Blocks Can Be Made in Space

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 9 Aug 2011 09:34:23 -0700 (PDT)
Message-ID: <201108091634.p79GYNRn026624_at_zagami.jpl.nasa.gov>

Aug. 8, 2011

Dwayne Brown
Headquarters, Washington
dwayne.c.brown at nasa.gov

Nancy Neal-Jones
Goddard Space Flight Center, Greenbelt, Md.
nancy.n.jones at nasa.gov
RELEASE: 11-263


WASHINGTON -- NASA-funded researchers have found more evidence
meteorites can carry DNA components created in space.

Scientists have detected the building blocks of DNA in meteorites
since the 1960s, but were unsure whether they were created in space
or resulted from contamination by terrestrial life. The latest
research indicates certain nucleobases -- the building blocks of our
genetic material -- reach the Earth on meteorites in greater
diversity and quantity than previously thought.

The discovery adds to a growing body of evidence that the chemistry
inside asteroids and comets is capable of making building blocks of
essential biological molecules. Previously, scientists found amino
acids in samples of comet Wild 2 from NASA's Stardust mission and in
various carbon-rich meteorites. Amino acids are used to make
proteins, the workhorse molecules of life. Proteins are used in
everything from structures such as hair to enzymes, which are the
catalysts that speed up or regulate chemical reactions.

The findings will be published in the online edition of the
Proceedings of the National Academy of Sciences. In the new work,
scientists analyzed samples of 12 carbon-rich meteorites, nine of
which were recovered from Antarctica. The team found adenine and
guanine, which are components of DNA nucleobases.

Also, in two of the meteorites, the team discovered for the first time
trace amounts of three molecules related to nucleobases that almost
never are used in biology. These nucleobase-related molecules, called
nucleobase analogs, provide the first evidence that the compounds in
the meteorites came from space and not terrestrial contamination.

"You would not expect to see these nucleobase analogs if contamination
from terrestrial life was the source, because they're not used in
biology," said Michael Callahan, astrobiologist and lead author of
the paper from NASA's Goddard Space Flight Center in Greenbelt, Md.
"However, if asteroids are behaving like chemical 'factories'
cranking out prebiotic material, you would expect them to produce
many variants of nucleobases, not just the biological ones, because
of the wide variety of ingredients and conditions in each asteroid."

Additional evidence came from research to further rule out the
possibility of terrestrial contamination as a source of these
molecules. The team analyzed an eight-kilogram (21.4-pound) sample of
ice from Antarctica, where most of the meteorites in the study were
found. The amounts of nucleobases found in the ice were much lower
than in the meteorites. More significantly, none of the nucleobase
analogs were detected in the ice sample. The team also analyzed a
soil sample collected near one of the non-Antarctic meteorite's fall
site. As with the ice sample, the soil sample had none of the
nucleobase analog molecules present in the meteorite.

Launched in Feb. 7, 1999, Stardust flew past an asteroid and traveled
halfway to Jupiter to collect particle samples from the comet Wild 2.
The spacecraft returned to Earth's vicinity to drop off a
sample-return capsule on January 15, 2006.

The research was funded by NASA's Astrobiology Institute at the
agency's Ames Research Laboratory in Moffett Field Calif., and the
Goddard Center for Astrobiology in Greenbelt, Md.; the NASA
Astrobiology Exobiology and Evolutionary Biology Program and the NASA
Postdoctoral Program at the agency's Headquarters in Washington.

Additional information and images are available at:

Received on Tue 09 Aug 2011 12:34:23 PM PDT

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