Organic Compounds on the Nucleus of Comet 67/Churyumov-Gerasimenko as Revealed by COSAC Mass Spectrometry

Description

The evolved gas analyzer COmetary SAmplingand Composition experiment (COSAC) aboardthe Philae Lander of ESA's Rosetta mission was designedto make unique in situ chemical analyses ofnucleus material from comet 67P/Churyumov-Gerasimenko, with an emphasis on organic molecules.Twenty-five minutes after Philae's initial touchdown,the COSAC mass spectrometer took a spectrum insniffing mode, which displayed an interesting suite oforganic compounds. The sampled material is likely tohave originated from the dust cloud produced by Philae'sfirst contact with the ground. Analysis of themass spectrum shows 16 compounds, among them sixdistinct organic homologous series: alcohols, carbonyls,amines, nitriles, amides and isocyanates. Nearlyall the molecules inferred from our data are potentialprecursors, products, adducts or by-products of eachother that can be formed either by surface reactions orby thermal and/or radiation processing of icy surfaces.A relatively abundant nitrogen source, such as NH3, isrequired to form the suite of N-bearing species. Severalorganic compounds have not been identified in cometsbefore or only upper limits have been derived. Overallthe identified compounds provide indications of severalpossible links between interstellar chemistry, cometaryorganic chemistry and terrestrial prebiotic chemistry.These unique COSAC measurements from a cometarysurface provide an unprecedented glimpse intothe early origins of our solar system, 4.6 billion yearsago.

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