An odd place for life's ingredients: asteroid may have made amino acids with water-free recipe.
Planetary scientists have found amino acids, the building blocks of proteins, in an unexpected place: a chunk of rock from an asteroid that formed at temperatures so high that such fragile organic compounds should have been destroyed. One explanation for the surprising discovery is that some amino acids might form through a mechanism that does not require water, says Daniel Glavin of NASA's Goddard Space Flight Center in Greenbelt, Md.
Analysis of a bit of asteroid 2008 [TC.sub.3], which fell to Earth over Sudan in 2008, suggests that the asteroid was once heated to temperatures exceeding 1,100[degrees] Celsius and was later subjected to a series of violent collisions with other asteroids, fusing different space rocks. Such an asteroid would be devoid of water, and the daughter chunk analyzed by Glavin's team would not be expected to form amino acids by any known mechanisms.
But the team did find amino acids in the rock that are either rare or nonexistent on Earth. More important, the two forms of the compounds--a left-handed structure and its mirror image--were equally common. Amino acids in life on Earth are predominantly left-handed.
"The pattern of amino acid abundances ... are hard to explain via terrestrial contamination," comments Conel Alexander of the Carnegie Institution for Science in Washington, D.C.
The extraterrestrial origin of these amino acids also can't be explained by a familiar process in which organic compounds react with ammonia, hydrogen cyanide and water to produce the protein building blocks.
The researchers describe their discovery online December 13 in Meteoritics & Planetary Science.
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|Title Annotation:||Atom & Cosmos|
|Article Type:||Brief article|
|Date:||Jan 29, 2011|
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