August 9, 2011

Evidence Shows Meteorites Carry DNA Components

Researchers found more evidence that meteorites can carry DNA components created in space.

The latest research indicates that certain nucleobases reach the Earth on meteorites in greater diversity and quantity than previously thought.

"People have been discovering components of DNA in meteorites since the 1960's, but researchers were unsure whether they were really created in space or if instead they came from contamination by terrestrial life," Dr. Michael Callahan of NASA's Goddard Space Flight Center, Greenbelt, Md said in a press release.

"For the first time, we have three lines of evidence that together give us confidence these DNA building blocks actually were created in space."

Callahan is lead author of a paper on the discovery appearing in Proceedings of the National Academy of Sciences (PNAS) of the United States of America.

The discovery is more evidence that the chemistry inside asteroids and comets is capable of making building blocks of essential biological molecules. 

Scientists found amino acids, which are used to make proteins, in samples of comet Wild 2 from NASA's Stardust mission. 

The researchers analyzed samples of 12 carbon-rich meteorites, nine of which came from Antarctica.  They found adenine and guanine, components of DNA nucleobases, among them.

The team also discovered trace amounts of three molecules related to nucleobases that are hardly ever used in biology.  These molecules 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," Callahan said in a statement.

"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."


Image Caption: Meteorites contain a large variety of nucleobases, an essential building block of DNA. (Artist concept credit: NASA's Goddard Space Flight Center/Chris Smith)


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