Removal of Titan's Atmospheric Noble Gases by their Sequestration in Surface Clathrates

Abstract

A striking feature of the atmosphere of Titan is that no heavy noble gases other than argon were detected by the Gas Chromatograph Mass Spectrometer (GCMS) aboard the Huygens probe during its descent to Titan's surface in January 2005. Here we provide an explanation of the mysterious absence or rarity of these noble gases in Titan's atmosphere: the thermodynamic conditions prevailing at the surface-atmosphere interface of the satellite allow the formation of multiple guest clathrates that preferentially store some species, including all heavy noble gases, over others. The clean water ice needed for formation of these clathrates could be delivered by successive episodes of cryovolcanic lavas that have been hypothesized to regularly cover the surface of Titan. The formation of clathrates in the porous lavas and their propensity for trapping Ar, Kr and Xe would progressively remove these species from the atmosphere of Titan over its history. In some circumstances, a global clathrate crust with an average thickness not exceeding a few meters could be sufficient on Titan for a complete removal of the heavy noble gases from the atmosphere.

Accepted for publication in The Astrophysical Journal Letters

References in corpus (7)

• The chemical composition of the Sun
• An estimate of the chemical composition of Titan's lakes
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Cited by in corpus (8)

• Titan's Atmosphere and Climate
• Methane clathrates in the Solar System
• Equilibrium composition between liquid and clathrate reservoirs on Titan
• Moderate D/H Ratios in Methane Ice on Eris and Makemake as Evidence of Hydrothermal or Metamorphic Processes in Their Interiors: Geochemical Analysis
• On the possible noble gas deficiency of Pluto's atmosphere
• In situ apparatus for the study of clathrate hydrates relevant to solar system bodies using synchrotron X-ray diffraction and Raman spectroscopy
• Open Questions and Future Directions in Titan Science
• Noble gas depletion on Titan: Clathrate sequestration during the open ocean phase