Thermodynamics of clathrate hydrate at low and high pressures with application to the outer solar system

Journal Article · Mon Jul 01 04:00:00 EDT 1985 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/191050· OSTI ID:5363872

Lunine, J I; Stevenson, D J

The thermodynamic stability of clathrate hydrate is calculated under a wide range of temperature and pressure conditions applicable to solar system problems, using a statistical mechanical theory developed by van der Waals an Platteeuw (1959) and existing experimental data on properties of clathrate hydrates and their components. At low pressure, dissociation pressures and partition functions (Langmuir constants) for CO clathrate (hydrate) have been predicted, using the properties of clathrate containing, as guests, molecules similar to CO. The comparable or higher propensity of CO to incorporate in clathrate relative to N/sub 2/ is used to argue for high CO-to-N/sub 2/ ratios in primordial Titan in N/sub 2/ was accreted as clathrate. The relative incorporation of noble gases in clathrate from a solar composition gas at low temperatures is calculated and applied to the case of giant-planet atmospheres and icy satellites. It is argued that nonsolar but well-constrained noble gas abundances will be measured by Galileo in the Jovian atmosphere if the observed carbon enhancement is due to bombardment of the atmosphere by clathrate- bearing planetesimals sometime after planetary formation. The noble gas abundances in Titan's atmosphere are also predicted under the hypothesis that much of the stellite's methane accreted a clathrate. Double occupancy of clathrate cages by H/sub 2/ and CH/sub 4/ in contact with a solar composition gas is examined, and it is concluded that potentially important amounts of H/sub 2/ may have incorporated in satellites as clathrate. The kinetics of clathrate formation is also examined, and it is suggested that, under thermodynamically appropriate conditions, essentially complete clathration of water ice could have occurred in high-pressure nebulae around giant planets but probably not in the outer solar nebula; comets probably did not aggregate as clathrate.

• Research Organization: Division of Geological and Planetary Sciences, California Institute of Technology
• OSTI ID: 5363872
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 58:3; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHEMICAL COMPOSITION
CHEMISTRY
CLATHRATES
COSMOCHEMISTRY
HYDRATES
MECHANICS
PLANETARY ATMOSPHERES
PRESSURE DEPENDENCE
STATISTICAL MECHANICS
SYNTHESIS
TEMPERATURE DEPENDENCE