Organic Compounds on the Nucleus of Comet 67/Churyumov-Gerasimenko as Revealed by COSAC Mass Spectrometry
Résumé
The evolved gas analyzer COmetary SAmpling
and Composition experiment (COSAC) aboard
the Philae Lander of ESA’s Rosetta mission was designed
to make unique in situ chemical analyses of
nucleus 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 in
sniffing mode, which displayed an interesting suite of
organic compounds. The sampled material is likely to
have originated from the dust cloud produced by Philae’s
first contact with the ground. Analysis of the
mass spectrum shows 16 compounds, among them six
distinct organic homologous series: alcohols, carbonyls,
amines, nitriles, amides and isocyanates. Nearly
all the molecules inferred from our data are potential
precursors, products, adducts or by-products of each
other that can be formed either by surface reactions or
by thermal and/or radiation processing of icy surfaces.
A relatively abundant nitrogen source, such as NH3, is
required to form the suite of N-bearing species. Several
organic compounds have not been identified in comets
before or only upper limits have been derived. Overall
the identified compounds provide indications of several
possible links between interstellar chemistry, cometary
organic chemistry and terrestrial prebiotic chemistry.
These unique COSAC measurements from a cometary
surface provide an unprecedented glimpse into
the early origins of our solar system, 4.6 billion years
ago.