On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko

Abstract

Primitive objects like comets hold important information on the material that formed our solar system. Several comets have been visited by spacecraft and many more have been observed through Earth-and space-based telescopes. Still our understanding remains limited. Molecular abundances in comets have been shown to be similar to interstellar ices and thus indicate that common processes and conditions were involved in their formation. The samples returned by the Stardust mission to comet Wild 2 showed that the bulk refractory material was processed by high temperatures in the vicinity of the early sun. The recent Rosetta mission acquired a wealth of new data on the composition of comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) and complemented earlier observations of other comets. The isotopic, elemental, and molecular abundances of the volatile, semivolatile, and refractory phases brought many new insights into the origin and processing of the incorporated material. The emerging picture after Rosetta is that at least part of the volatile material was formed before the solar system and that cometary nuclei agglomerated over a wide range of heliocentric distances, different from where they are found today. Deviations from bulk solar system abundances indicate that the material was not fully homogenized at the location of comet formation, despite the radial mixing implied by the Stardust results. Post-formation evolution of the material might play an important role, which further

Tracing the Formation History of Giant Planets in Protoplanetary Disks with Carbon, Oxygen, Nitrogen, and Sulfur

“…The observations of the composition of comet 67P Churyumov-Gerasimenko (67P C-G in the following) by the ESA mission Rosetta provide further support for the leading role of refractory materials as the main carrier of S, in agreement with the results of Kama et al (2019). Rosetta's observations show a relative abundance of H 2 S, the main volatile carrier of S, of the order of 10 −2 that of water (Le Roy et al 2015;Rubin et al 2019Rubin et al , 2020. In our compositional model, this amounts to ∼10% of the solar budget of S (see text below, as well as Table 2 and Figure 3).…”

Distant Formation and Differentiation of Outer Main Belt Asteroids and Carbonaceous Chondrite Parent Bodies

“…The model composition of Case 3 was established by considering comets as a reference. There is no significant bulk compositional variation between comets from the Kuiper belt or from the Oort cloud, and the abundances of CO 2 , NH 3 , and H 2 S relative to H 2 O range 2%–30%, 0.3%–1%, and 0.3%–1%, respectively (the number of samples is about 10, Bockelée‐Morvan & Biver, 2017; Mumma & Charnley, 2011; M. Rubin et al., 2020). We assumed roughly averaged values in Case 3.…”

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“…H 2 O, CO 2 , CO, CH 4 ), our understanding of which has been significantly evolving over the past decade thanks to the data provided by meteorites, comets, polluted white dwarfs, and protoplanetary discs (e.g. [72,74,75,222,236,261,[289][290][291][292][293][294][295][296][297][298][299][300]), and the extension of the planet-forming region in discs, recently put into question by observational surveys of protoplanetary discs with ALMA (e.g. [68,[301][302][303][304][305]).…”