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/Halley1,2. Such matter is generally thought to have originated in the interstellar medium3, but it might have formed in the solar nebula—the cloud of gas and dust that was left over after the Sun formed4. This solid carbonaceous material cannot be observed from Earth, so it has eluded unambiguous characterization5. Many gaseous organic molecules, however, have been observed6,7,8,9; they come mostly from the sublimation of ices at the surface or in the subsurface of cometary nuclei8. These ices could have been formed from material inherited from the interstellar medium that suffered little processing in the solar nebula10. 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 meteorites11,12. 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 bodies11. 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.
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COSIMA was built by a consortium led by the Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany, in collaboration with: the Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, Orléans, France; the Institut d’Astrophysique Spatiale, CNRS/Université Paris Sud, Orsay, France; the Finnish Meteorological Institute, Helsinki, Finland; the Universität Wuppertal, Wuppertal, Germany; von Hoerner und Sulger GmbH, Schwetzingen, Germany; the Universität der Bundeswehr, Neubiberg, Germany; the Institut für Physik, Forschungszentrum Seibersdorf, Seibersdorf, Austria; and the Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften, Graz, Austria; and is led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany. We acknowledge the support of the national funding agencies of Germany (Deutsches Zentrum für Luft- und Raumfahrt (DLR), grant 50 QP 1302), France (Centre National d’Étude Spatiales (CNES)), Austria, Finland and the European Space Agency (ESA) Technical Directorate. A.B. acknowledges support from the CNES and the Labex Exploration Spatiale des Environnements Planétaires (ESEP; no. 2011-LABX-030), and funding from the Idex Paris Sciences et Lettres (PSL; no. ANR-10-IDEX-0001-02). S.S. acknowledges support from the Swedish National Space Board grant (contracts 121/11 and 198/15). H.L., B.Z. and K.L. acknowledge Academy of Finland grant 277375. We thank the Rosetta Science Ground Segment at the European Space Astronomy Centre, the Rosetta Mission Operations Centre at the European Space Operations Centre, and the Rosetta Project at the European Space Research and Technology Centre for their work, which enabled the scientific return of the Rosetta mission.