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article imageMeteorites brought building blocks of life to earth

By Elizabeth Cunningham Perkins     Aug 8, 2011 in Science
Scientists studying meteorites -- space rocks big enough to survive the tumble to earth, carrying chemicals that swirled in our solar system's primeval days -- announced they identified life's building blocks on carbonaceous chondrite samples.
Scientists have tried to prove since the 1960s that the genetic building blocks called nucleobases rode to earth on meteorites, like protein's building blocks the amino acids did, but evidence was not definitive until new research, to be published later this month in the the Proceedings of the National Academy of Sciences, demonstrated large, diverse amounts of nucleobases do indeed piggyback to earth on carbonaceous chondrite meteorites, Carnegie’s Geophysical Laboratory and NASA reported:
Using advanced spectroscopy, the astrobiologists analyzed purified samples from 11 carbonaceous chondrites and one ureilite, a rare, stony achondrite meteorite (without chondrules), a first-time examination for nucleobases for all but two of these extraterrestrial rocks.
Two carbonaceous chondrites contained many different nucleobases and structurally similar molecules called nucleobase analogs, none of which are commonly found in soil or ice on earth, and all of which were scarce in ice and soil samples taken from the areas where the meteorites were collected, suggesting an extraterrestrial origin, the researchers concluded.
To test this conclusion, the team designed experiments to reproduce nucleobases and analogs from chemical reactions of cyanide and ammonia, two chemicals that are often present in space. The resulting lab-synthesized nucleobases differed from those found in the meteorites mainly in relative abundances, possibly because of heat and chemicals encountered by meteorite-origin nucleobases during space travel, the scientists theorized.
The results of this new research strongly imply that some or all of this planet's earliest lifeforms may have self-assembled from meteoric molecular "tool kits" that streaked down from the sky, the astrobiologists claim.
Previous research, led by a geologist at the University of Alberta, on the Tagish Lake, British Columbia meteorite collected in 2000, revealed its organic compounds had evolved during travels around the early solar system, ScienceDaily reported in June 2011.
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