Meteoriti rivelano altri metodi di assemblaggio delle componenti della vita. Nuove scoperte su "Meteoritics and Planetary Science".
Gli elementi costitutivi della vita possono assemblarsi in diversi modi. La nuova ricerca condotta dalla NASA (Astrobiology Analytical Laboratory, Goddard Space Flight Center di Greenbelt, nel Maryland) si basa sui dati raccolti su 14 a meteoriti trovati in Antartide, come quello nella foto a sinistra (credits: Antarctic Search for Meteorites program, Case Western Reserve University). Questi meteoriti sono ricchi di carbonio, aminoacidi e minerali. In particolare questi ultimi risultavano essere stati sottoposti a temperature superiori a 1100 gradi centigradi. In precedenza gli amminoacidi erano stati creati a partire da acqua, aldeidi, chetoni, ammoniaca e cianidrine implicate nella sintesi di Strecker rinvenuti in meteoriti che risultavano essere stati stati creati a temperature basse.
«Anche se avevamo già trovato amminoacidi - ha dichiarato Aaron Burton, ricercatore della NASA (nella foto) - in meteoriti ricchi di carbonio, non ci aspettavamo di trovare proprio questi gruppi, in quanto le alte temperature normalmente tendono a distruggere gli aminoacidi. Tuttavia, il tipo di amminoacidi abbiamo che scoperto in questi meteoriti indica che sono stati prodotti da un diverso, ad alta temperatura di processo come loro asteroidi madri gradualmente raffreddato».
Burton è autore di un articolo su questa scoperta pubblicato su Meteoritics and Planetary Science nel quale viene identificato nei 14 meteoriti soggetti a alterazioni termiche: A propensity for n-ω-amino acids in thermally altered Antarctic meteorites
Abstract
Asteroids and their fragments have impacted the Earth for the last 4.5 Gyr. Carbonaceous meteorites are known to contain a wealth of indigenous organic molecules, including amino acids, which suggests that these meteorites could have been an important source of prebiotic organic material during the origins of life on Earth and possibly elsewhere. We report the detection of extraterrestrial amino acids in thermally altered type 3 CV and CO carbonaceous chondrites and ureilites recovered from Antarctica. The amino acid concentrations of the thirteen Antarctic meteorites ranged from 300 to 3200 parts-per-billion (ppb), generally much less abundant than in amino acid-rich CI, CM, and CR carbonaceous chondrites that experienced much lower temperature aqueous alteration on their parent bodies. In contrast to low-temperature aqueously altered meteorites that show complete structural diversity in amino acids formed predominantly by Strecker–cyanohydrin synthesis, the thermally altered meteorites studied here are dominated by small, straight-chain, amine terminal (n-ω-amino) amino acids that are not consistent with Strecker formation. The carbon isotopic ratios of two extraterrestrial n-ω-amino acids measured in one of the CV chondrites (δ13C approximately −25‰) are consistent with 13C-depletions observed previously in hydrocarbons produced by Fischer-Tropsch type reactions. The predominance of n-ω-amino acid isomers in thermally altered meteorites hints at cosmochemical mechanisms for the preferential formation and preservation of a small subset of the possible amino acids.
Meteorites Reveal Another Way to Make Life's Components
«Anche se avevamo già trovato amminoacidi - ha dichiarato Aaron Burton, ricercatore della NASA (nella foto) - in meteoriti ricchi di carbonio, non ci aspettavamo di trovare proprio questi gruppi, in quanto le alte temperature normalmente tendono a distruggere gli aminoacidi. Tuttavia, il tipo di amminoacidi abbiamo che scoperto in questi meteoriti indica che sono stati prodotti da un diverso, ad alta temperatura di processo come loro asteroidi madri gradualmente raffreddato».
Burton è autore di un articolo su questa scoperta pubblicato su Meteoritics and Planetary Science nel quale viene identificato nei 14 meteoriti soggetti a alterazioni termiche: A propensity for n-ω-amino acids in thermally altered Antarctic meteorites
Abstract
Asteroids and their fragments have impacted the Earth for the last 4.5 Gyr. Carbonaceous meteorites are known to contain a wealth of indigenous organic molecules, including amino acids, which suggests that these meteorites could have been an important source of prebiotic organic material during the origins of life on Earth and possibly elsewhere. We report the detection of extraterrestrial amino acids in thermally altered type 3 CV and CO carbonaceous chondrites and ureilites recovered from Antarctica. The amino acid concentrations of the thirteen Antarctic meteorites ranged from 300 to 3200 parts-per-billion (ppb), generally much less abundant than in amino acid-rich CI, CM, and CR carbonaceous chondrites that experienced much lower temperature aqueous alteration on their parent bodies. In contrast to low-temperature aqueously altered meteorites that show complete structural diversity in amino acids formed predominantly by Strecker–cyanohydrin synthesis, the thermally altered meteorites studied here are dominated by small, straight-chain, amine terminal (n-ω-amino) amino acids that are not consistent with Strecker formation. The carbon isotopic ratios of two extraterrestrial n-ω-amino acids measured in one of the CV chondrites (δ13C approximately −25‰) are consistent with 13C-depletions observed previously in hydrocarbons produced by Fischer-Tropsch type reactions. The predominance of n-ω-amino acid isomers in thermally altered meteorites hints at cosmochemical mechanisms for the preferential formation and preservation of a small subset of the possible amino acids.
Meteorites Reveal Another Way to Make Life's Components
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