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

[Ron Baalke]

Aug. 8, 2011

Dwayne Brown 
Headquarters, Washington                                         
202-358-1726 
dwayne.c.brown at nasa.gov 

Nancy Neal-Jones 
Goddard Space Flight Center, Greenbelt, Md. 
301-286-0039 
nancy.n.jones at nasa.gov 
RELEASE: 11-263

NASA RESEARCH SHOWS DNA BUILDING BLOCKS CAN BE MADE IN SPACE

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: 

http://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html 
	
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