High-molecular-weight organic matter in the particles of comet 67P/Churyumov–Gerasimenko

• Published in: Nature (London) Vol. 538; no. 7623; pp. 72 - 74
• Main Authors: Fray, Nicolas, Bardyn, Anaïs, Cottin, Hervé, Altwegg, Kathrin, Baklouti, Donia, Briois, Christelle, Colangeli, Luigi, Engrand, Cécile, Fischer, Henning, Glasmachers, Albrecht, Grün, Eberhard, Haerendel, Gerhard, Henkel, Hartmut, Höfner, Herwig, Hornung, Klaus, Jessberger, Elmar K., Koch, Andreas, Krüger, Harald, Langevin, Yves, Lehto, Harry, Lehto, Kirsi, Le Roy, Léna, Merouane, Sihane, Modica, Paola, Orthous-Daunay, François-Régis, Paquette, John, Raulin, François, Rynö, Jouni, Schulz, Rita, Silén, Johan, Siljeström, Sandra, Steiger, Wolfgang, Stenzel, Oliver, Stephan, Thomas, Thirkell, Laurent, Thomas, Roger, Torkar, Klaus, Varmuza, Kurt, Wanczek, Karl-Peter, Zaprudin, Boris, Kissel, Jochen, Hilchenbach, Martin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06-10-2016; Nature Publishing Group
• Subjects: 639/33/445/3928; 639/33/445/848; Asteroids; Astrophysics; Atoms & subatomic particles; Comets; Dust; Humanities and Social Sciences; Kuiper belt; letter; multidisciplinary; Organic chemicals; Organic matter; Science; Sciences of the Universe; Sublimation
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature19320

The COSIMA mass spectrometer on the Rosetta spacecraft has analysed the solid organic matter found in dust particles emitted by comet 67P/Churyumov–Gerasimenko; this matter is similar to the insoluble organic matter extracted from carbonaceous chondrites such as the Murchison meteorite, but is perhaps more primitive.
Organic matter on comet 67P
The COSIMA mass spectrometer on board the ESA Rosetta spacecraft has detected more than 27,000 particles in the vicinity of comet 67P/Churyumov–Gerasimenko. Of these, more than 200 particles have been analysed so far and this paper presents further chemical analysis of two of these particles, dubbed Kenneth and Juliette. The results reveal the presence of solid organic matter, in which the carbon is bound in very large macromolecular compounds, analogous to the insoluble organic matter found in the carbonaceous chondrite meteorites. The authors conclude that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but has suffered less modification before and/or after incorporation in the comet.
The presence of solid carbonaceous matter in cometary dust was established by the detection of elements such as carbon, hydrogen, oxygen and nitrogen in particles from comet 1P/Halley
1
,
2
. Such matter is generally thought to have originated in the interstellar medium
3
, but it might have formed in the solar nebula—the cloud of gas and dust that was left over after the Sun formed
4
. This solid carbonaceous material cannot be observed from Earth, so it has eluded unambiguous characterization
5
. Many gaseous organic molecules, however, have been observed
6
,
7
,
8
,
9
; they come mostly from the sublimation of ices at the surface or in the subsurface of cometary nuclei
8
. These ices could have been formed from material inherited from the interstellar medium that suffered little processing in the solar nebula
10
. Here we report the
in situ
detection of solid organic matter in the dust particles emitted by comet 67P/Churyumov–Gerasimenko; the carbon in this organic material is bound in very large macromolecular compounds, analogous to the insoluble organic matter found in the carbonaceous chondrite meteorites
11
,
12
. The organic matter in meteorites might have formed in the interstellar medium and/or the solar nebula, but was almost certainly modified in the meteorites’ parent bodies
11
. We conclude that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before and/or after being incorporated into the comet.