A protosolar nebula origin for the ices agglomerated by Comet 67P/Churyumov-Gerasimenko

Abstract

The nature of the icy material accreted by comets during their formation in the outer regions of the protosolar nebula is a major open question in planetary science. Some scenarios of comet formation predict that these bodies agglomerated from crystalline ices condensed in the protosolar nebula. Concurrently, alternative scenarios suggest that comets accreted amorphous ice originating from the interstellar cloud or from the very distant regions of the protosolar nebula. On the basis of existing laboratory and modeling data, we find that the N${}_2$/CO and Ar/CO ratios measured in the coma of the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA instrument aboard the European Space Agency's Rosetta spacecraft match those predicted for gases trapped in clathrates. If these measurements are representative of the bulk N${}_2$/CO and Ar/CO ratios in 67P/Churyumov-Gerasimenko, it implies that the ices accreted by the comet formed in the nebula and do not originate from the interstellar medium, supporting the idea that the building blocks of outer solar system bodies have been formed from clathrates and possibly from pure crystalline ices. Moreover, because 67P/Churyumov-Gerasimenko is impoverished in Ar and N${}_2$, the volatile enrichments observed in Jupiter's atmosphere cannot be explained solely via the accretion of building blocks with similar compositions and require an additional delivery source. A potential source may be the accretion of gas from the nebula that has been progressively enriched in heavy elements due to photoevaporation.

arXiv commentThe Astrophysical Journal Letters, in press

References in corpus (11)

• Abundances of the elements in the solar system
• Oort Cloud and Scattered Disc formation during a late dynamical instability in the Solar System
• Jupiter's composition: sign of a (relatively) late formation in a chemically evolved protosolar disk
• The chemical history of molecules in circumstellar disks. II. Gas-phase species
• Clathration of Volatiles in the Solar Nebula and Implications for the Origin of Titan's atmosphere
• Volatile inventories in clathrate hydrates formed in the primordial nebula
• Nebular water depletion as the cause of Jupiter's low oxygen abundance
• On the formation location of Uranus and Neptune as constrained by dynamical and chemical models of comets
• The Phases of Water Ice in the Solar Nebula
• A $\sim$32-70 K formation temperature range for the ice grains agglomerated by comet 67P/Churyumov-Gerasimenko
• New insights on Saturn's formation from its nitrogen isotopic composition

Cited by in corpus (16)

• The Rosetta mission orbiter Science overview the comet phase
• Deep Atmosphere Composition, Structure, Origin, and Exploration, with Particular Focus on Critical in situ Science at the Icy Giants
• The Role of Ice Compositions for Snowlines and the C/N/O Ratios in Active Disks
• Origin of molecular oxygen in Comet 67P/Churyumov-Gerasimenko
• Jupiter's formation in the vicinity of the amorphous ice snowline
• Primordial N2 provides a cosmochemical explanation for the existence of Sputnik Planitia, Pluto
• Entrapment of CO in CO2 ice
• Moderate D/H Ratios in Methane Ice on Eris and Makemake as Evidence of Hydrothermal or Metamorphic Processes in Their Interiors: Geochemical Analysis
• The Effect of Protoplanetary Disk Cooling Times on the Formation of Gas Giant Planets by Gravitational Instability
• Impact of radiogenic heating on the formation conditions of comet 67P/Churyumov-Gerasimenko
• Key Atmospheric Signatures for Identifying the Source Reservoirs of Volatiles in Uranus and Neptune
• Stability of sulphur dimers S2 in cometary ices
• The Efficiency of Noble Gas Trapping in Astrophysical Environments
• A gas-phase primordial origin of O2 in comet 67P/Churyumov-Gerasimenko
• Ionic emissions in comet C/2016 R2 (Pan-STARRS)
• What is Neptune's D/H ratio really telling us about its water abundance ?