Kinetics of methane clathrate formation and dissociation under Mars relevant conditions

Gainey, S. R.; Madden, M. E. Elwood

doi:10.1016/j.icarus.2011.12.019

Cited by 35 publications

(17 citation statements)

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“…If the time scales of trapping in clathrates and of transfer throughout the ocean are shorter, this would strongly point to a steady methane production at approximately the plumes' ejection rate. The experimental methane entrapping rates [ Gainey and Elwood Madden , ], applied to the surface of the South Polar Region, suggest a yearly methane entrapping that is 40,000 times the amount of methane ejected in the plumes (assuming a plume rate of 350 kg/s) over the same time scale. Additionally, numerical simulations for Europa's internal ocean [ Goodman and Lenferink , ] indicate that hydrothermal activity generates ascending currents at a speed of 1–5 cm/s, giving a transfer time scale well below a year.…”

Section: Resultsmentioning

confidence: 99%

Possible evidence for a methane source in Enceladus' ocean

Bouquet

Mousis

Waite

et al. 2015

Geophysical Research Letters

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International audienceThe internal ocean of Enceladus can be expected to present conditions favorable to the trapping of volatiles in clathrates. This process could influence the eventual composition of the ocean and therefore of the plumes emitted by the south polar region. Here we used a statistical thermodynamic model to assess which species detected in the plumes by the Cassini-Ion and Neutral Mass Spectrometer experiment are trapped in clathrates. We treated Enceladus' internal ocean as a terrestrial subglacial lake with a mixture of dissolved volatiles indicated by plume gas measurements. We find that the conditions for clathrate formation are met in this ocean, except above 20km or in hypothetical hot spots. The formation of multiple guest clathrates depletes methane below plume levels, suggesting that clathrates eventually dissociate (releasing methane) in the fissure that connects the ocean to the surface or that another mechanism (such as hydrothermal reactions) is compensating by adding methane into the ocean

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Section: Resultsmentioning

confidence: 99%

Possible evidence for a methane source in Enceladus' ocean

Bouquet

Mousis

Waite

et al. 2015

Geophysical Research Letters

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“…Several experimental studies have tried to quantify the flux of methane from a destabilized column of methane hydrate (Takeya et al 2001;Sun & Chen 2006;Gainey & Elwood Madden 2012), though for conditions not entirely consistent with those for water planets. Therefore, we develop physical arguments to help us extrapolate the experimental data.…”

Section: Ch 4 Outgassing Fluxmentioning

confidence: 99%

STRUCTURE AND DYNAMICS OF COLD WATER SUPER-EARTHS: THE CASE OF OCCLUDED CH₄AND ITS OUTGASSING

Levi

Sasselov

Podolak

2014

ApJ

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In this work, we study the transport of methane in the external water envelopes surrounding water-rich super-Earths. We investigate the influence of methane on the thermodynamics and mechanics of the water mantle. We find that including methane in the water matrix introduces a new phase (filled ice), resulting in hotter planetary interiors. This effect renders the super-ionic and reticulating phases accessible to the lower ice mantle of relatively low-mass planets (∼5 M E ) lacking a H/He atmosphere. We model the thermal and structural profile of the planetary crust and discuss five possible crustal regimes which depend on the surface temperature and heat flux. We demonstrate that the planetary crust can be conductive throughout or partly confined to the dissociation curve of methane clathrate hydrate. The formation of methane clathrate in the subsurface is shown to inhibit the formation of a subterranean ocean. This effect results in increased stresses on the lithosphere, making modes of ice plate tectonics possible. The dynamic character of the tectonic plates is analyzed and the ability of this tectonic mode to cool the planet is estimated. The icy tectonic plates are found to be faster than those on a silicate super-Earth. A mid-layer of low viscosity is found to exist between the lithosphere and the lower mantle. Its existence results in a large difference between ice mantle overturn timescales and resurfacing timescales. Resurfacing timescales are found to be 1 Ma for fast plates and 100 Ma for sluggish plates, depending on the viscosity profile and ice mass fraction. Melting beneath spreading centers is required in order to account for the planetary radiogenic heating. The melt fraction is quantified for the various tectonic solutions explored, ranging from a few percent for the fast and thin plates to total melting of the upwelled material for the thick and sluggish plates. Ice mantle dynamics is found to be important for assessing the composition of the atmosphere. We propose a mechanism for methane release into the atmosphere, where freshly exposed reservoirs of methane clathrate hydrate at the ridge dissociate under surface conditions. We formulate the relation between the outgassing flux and the tectonic mode dynamical characteristics. We give numerical estimates for the global outgassing rate of methane into the atmosphere. We find, for example, that for a 2 M E planet outgassing can release 10 27 -10 29 molecules s −1 of methane to the atmosphere. We suggest a qualitative explanation for how the same outgassing mechanism may result in either a stable or a runaway volatile release, depending on the specifics of a given planet. Finally, we integrate the global outgassing rate for a few cases and quantify how the surface atmospheric pressure of methane evolves over time. We find that methane is likely an important constituent of water planets' atmospheres.

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“…Theoretical and experimental studies of methane clathrates kinetics indicate dissociation rates ranging from 3 Â 10 À6 to 1 Â 10 À4 mol m À2 s À1 (Gainey and Madden, 2012), while the diffusion rates of the molecules through ice or clathrates are much lower, spanning a large range of order of magnitudes from 4 Â 10 À6 to 10 À15 mol m À2 s À1 (Mousis et al, 2013 and references therein). Such values are consistent with the possibility for deep underground martian clathrates to have remained stable over long timescales of the planet, but they remain poorly constrained and need to be better studied in the future.…”

Section: Discussionmentioning

confidence: 99%

Methane storage capacity of the early martian cryosphere

Lasue

Quesnel

Langlais

et al. 2015

Icarus

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Kinetics of methane clathrate formation and dissociation under Mars relevant conditions

Cited by 35 publications

References 50 publications

Possible evidence for a methane source in Enceladus' ocean

Possible evidence for a methane source in Enceladus' ocean

STRUCTURE AND DYNAMICS OF COLD WATER SUPER-EARTHS: THE CASE OF OCCLUDED CH₄AND ITS OUTGASSING

Methane storage capacity of the early martian cryosphere

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Kinetics of methane clathrate formation and dissociation under Mars relevant conditions

Cited by 35 publications

References 50 publications

Possible evidence for a methane source in Enceladus' ocean

Possible evidence for a methane source in Enceladus' ocean

STRUCTURE AND DYNAMICS OF COLD WATER SUPER-EARTHS: THE CASE OF OCCLUDED CH4AND ITS OUTGASSING

Methane storage capacity of the early martian cryosphere

Contact Info

Product

Resources

About

STRUCTURE AND DYNAMICS OF COLD WATER SUPER-EARTHS: THE CASE OF OCCLUDED CH₄AND ITS OUTGASSING