Research ArticleSPACE SCIENCES

The presence of clathrates in comet 67P/Churyumov-Gerasimenko

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Science Advances  08 Apr 2016:
Vol. 2, no. 4, e1501781
DOI: 10.1126/sciadv.1501781
  • Fig. 1 Equilibrium curves of clathrates and condensation in the PSN.

    Equilibrium curves of C2H6 (red) and CH4 (blue) clathrates are shown with respect to the equilibrium curves of C2H6, CH4, and CO2 ices (black dashed lines) as a function of total nebular pressure. The arrow indicates the direction of cooling in the PSN. Above the clathrate stability/condensation curve, a volatile species exists in the gas phase. Below the clathrate stability/condensation curve, a volatile species may form clathrates or pure condensates. The gas-phase mole fractions relative to H2 were derived from the cometary X/H2O ratios (14) and solar system elemental abundances of O and H (40, 41).

  • Fig. 2 Equilibrium curves of clathrates and pure condensates in the cometary environment.

    The equilibrium curves are shown here as a function of total H2O pressure. Decomposition of the clathrate structures and sublimation of pure ices occur at temperatures above the equilibrium curves, whereas clathrates/pure condensates remain stable below the curves. Mole fractions of each species shown are directly taken from ROSINA/DFMS measurements of the coma of 67P (14).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/4/e1501781/DC1

    Fig. S1. Time variation of major and minor volatile species from ROSINA/DFMS on 18 September 2014.

    Fig. S2. Time variation of major and minor volatile species from ROSINA/DFMS on 29 September 2014.

    Fig. S3. Time variation of major and minor volatile species from ROSINA/DFMS on 11 October 2014.

    Fig. S4. Equilibrium curves in the PSN for various known comets.

    Table S1. Fitting parameters used in calculating clathrate equilibrium curves of CH4 and C2H6.

    Table S2. Fitting coefficients used to calculate condensation curves.

    Table S3. Fitting coefficients for the condensation pressure of crystalline H2O ice.

    References (42, 43)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Time variation of major and minor volatile species from ROSINA/DFMS on 18 September 2014.
    • Fig. S2. Time variation of major and minor volatile species from ROSINA/DFMS on 29 September 2014.
    • Fig. S3. Time variation of major and minor volatile species from ROSINA/DFMS on 11 October 2014.
    • Fig. S4. Equilibrium curves in the PSN for various known comets.
    • Table S1. Fitting parameters used in calculating clathrate equilibrium curves of CH4 and C2H6.
    • Table S2. Fitting coefficients used to calculate condensation curves.
    • Table S3. Fitting coefficients for the condensation pressure of crystalline H2O ice.
    • References (42, 43)

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