Noble Gas Abundance Ratios Indicate the Agglomeration of 67P/Churyumov-Gerasimenko from Warmed-up Ice

Research output: Contribution to journalArticle

Abstract

The origin of cometary volatiles remains a major open question in planetary science. Comets may have either agglomerated from crystalline ices condensed in the protosolar nebula (PSN) or from amorphous ice originating from the molecular cloud and interstellar medium. Here, based on the recent argon, krypton, and xenon measurements performed by the ROSINA mass spectrometer on board the European Space Agency's Rosetta spacecraft in the coma of 67P/Churyumov-Gerasimenko, we show that these noble gas relative abundances can be explained if the comet's building blocks formed from a mixture of gas and H2O grains resulting from the annealing of pristine amorphous ice (i.e., originating from the presolar cloud) in the PSN. In this scenario, the different volatiles released during the amorphous-to-crystalline ice phase transition would have been subsequently trapped at lower temperatures in stoichiometric hydrate or clathrate hydrate forms by the crystalline water ice generated by the transition. Once crystalline water was completely consumed by clathration in the ∼25-80 K temperature range, the volatile species remaining in the gas phase would have formed pure condensates at lower temperatures. The formation of clathrates hydrates and pure condensates to explain the noble gas relative abundances is consistent with a proposed interstellar origin of molecular oxygen detected in 67P/Churyumov-Gerasimenko, and with the measured molecular nitrogen depletion in comets.

Details

Authors
  • O. Mousis
  • T. Ronnet
  • J. I. Lunine
  • A. Luspay-Kuti
  • K. E. Mandt
  • G. Danger
  • F. Pauzat
  • Y. Ellinger
  • P. Wurz
  • P. Vernazza
  • L. Le Sergeant D'Hendecourt
External organisations
  • Laboratoire d'Astrophysique de Marseille (LAM)
  • Cornell University
  • Johns Hopkins University
  • Physics of Ionic and Molecular Interactions
  • Versailles Saint-Quentin-en-Yvelines University
  • University of Bern
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • astrobiology, comets: general, comets: individual (67P/Churyumov-Gerasimenko), methods: numerical, solid state: volatile
Original languageEnglish
Article numberL11
JournalAstrophysical Journal Letters
Volume865
Issue number1
Publication statusPublished - 2018 Sep 20
Publication categoryResearch
Peer-reviewedYes
Externally publishedYes