131 for Figure 1 (right). A blank sample consisted of an MgF2
window, on which the H2O/13CH3OH/NH3 gas mixture was deposit-
ed at 80 K, while not irradiating with UV light. The blank sample
was submitted to the entire analytical protocol, in which no amino
acids and diamino acids were detected (Figure S3). The quantum
yields obtained are very similar to previous experiments.[14]
cules including amino acids using circularly polarized electro-
magnetic radiation have been performed to study enantiose-
lective photolysis[23] which may be at the origin of biomolecu-
lar homochirality.[24] Circularly polarized light of the same helici-
ty over large distance scales has been detected in interstellar
molecular clouds,[25] and recently the first promising experi-
ments simulating amino acid formation under interstellar con-
ditions induced a significant enantiomeric excess of 1.3% into
the amino acid a-alanine.[26]
Acknowledgements
This study was supported by the Agence Nationale de la Recher-
che (ANR-07-BLAN-0293) and the Centre National d’Etudes Spa-
tiales (CNES).
The obtained results let us conclude that the formation of
organic compounds of prebiotic interest in interstellar/proto-
stellar environments[27] followed by their delivery by meteor-
ites, interplanetary dust particles, or by comets[9] to the early
Earth represents a plausible astro-physicochemical scenario for
the appearance of life on Earth.[28] We found a molecular reser-
voir of amino acid species which, together with complementa-
ry sources, might have preceded and triggered the formation
of proto-proteins and peptide-based nucleic acid analogues on
the early Earth, and which we explicitly interpret as an inter-
mediate state of the evolution of life. The reported identifica-
tion of 20 amino acids and six diamino acids in a sample of an
interstellar ice analogue is of importance for all scenarios de-
scribing the appearance of life on Earth on the molecular level.
Moreover the scientific objectives of the cometary Rosetta
Lander Philae will benefit from these data. Philae includes the
Cometary Sampling and Composition (COSAC) instrument,
which is an enantioselective GC-TOFMS designed to identify
organic molecules including chiral amino acids in cometary
ices after landing on a cometary nucleus in 2015.[4,15]
Keywords: amino acids
·
chirality
·
comets
·
gas
chromatography · origins of life
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Experimental Section
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