The Putative Cerean Exosphere

Norbert Schorghofer, Shane Byrne, Margaret E. Landis, Erwan Mazarico, Thomas H. Prettyman, Britney E. Schmidt, Michaela N. Villarreal, Julie Castillo-Rogez, Carol A. Raymond, Christopher T. Russell

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

The ice-rich crust of dwarf planet 1 Ceres is the source of a tenuous water exosphere, and the behavior of this putative exosphere is investigated with model calculations. Outgassing water molecules seasonally condense around the winter pole in an optically thin layer. This seasonal cap reaches an estimated mass of at least 2 × 103 kg, and the aphelion summer pole may even retain water throughout summer. If this reservoir is suddenly released by a solar energetic particle event, it would form a denser transient water exosphere. Our model calculations also explore species other than H2O. Light exospheric species escape rapidly from Ceres due to its low gravity, and hence their exospheres dissipate soon after their respective source has faded. For example, the theoretical turn-over time in a water exosphere is only 7 hr. A significant fraction of CO2 and SO2 molecules can get trapped and stored in perennially shadowed regions at the current spin axis orientation, but not at the higher spin axis tilt, leaving H2O as the only common volatile expected to accumulate in polar cold traps over long timescales. The D/H fractionation during migration to the cold traps is only about 10%.

Original languageEnglish (US)
Article number85
JournalAstrophysical Journal
Volume850
Issue number1
DOIs
StatePublished - Nov 20 2017

Keywords

  • asteroids: individual (Ceres)
  • minor planets
  • molecular processes
  • solid state: volatile

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Schorghofer, N., Byrne, S., Landis, M. E., Mazarico, E., Prettyman, T. H., Schmidt, B. E., Villarreal, M. N., Castillo-Rogez, J., Raymond, C. A., & Russell, C. T. (2017). The Putative Cerean Exosphere. Astrophysical Journal, 850(1), [85]. https://doi.org/10.3847/1538-4357/aa932f