The Experts below are selected from a list of 3411 Experts worldwide ranked by ideXlab platform
Amit Levi - One of the best experts on this subject based on the ideXlab platform.
-
structure and dynamics of cold water super earths the case of occluded ch4 and its outgassing
The Astrophysical Journal, 2014Co-Authors: Amit Levi, Dimitar D Sasselov, M PodolakAbstract: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{sub 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 lowmore » 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{sub E} planet outgassing can release 10{sup 27}-10{sup 29} molecules s{sup –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.« less
-
structure and dynamics of cold water super earths the case of occluded ch4 and its outgassing
arXiv: Earth and Planetary Astrophysics, 2014Co-Authors: Amit Levi, Dimitar D Sasselov, M PodolakAbstract:We study the transport of methane in the external water envelopes surrounding water-rich super-Earths and estimate its outgassing into the atmosphere. 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 relatively low mass planets lacking a H/He atmosphere. We model the thermal and structural profile of the Planetary Crust and discuss five possible Crustal regimes. 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 dynamics of the tectonic plates are analysed. We derive overturn and resurfacing time scales as well as the melt fraction underneath spreading centers. Ice mantle dynamics is found to be important for assessing the composition of the atmosphere. We formulate the relation between the outgassing flux of methane and the tectonic mode dynamics. We give numerical estimates for the global outgassing rate of methane into the atmosphere.
M Podolak - One of the best experts on this subject based on the ideXlab platform.
-
structure and dynamics of cold water super earths the case of occluded ch4 and its outgassing
The Astrophysical Journal, 2014Co-Authors: Amit Levi, Dimitar D Sasselov, M PodolakAbstract: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{sub 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 lowmore » 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{sub E} planet outgassing can release 10{sup 27}-10{sup 29} molecules s{sup –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.« less
-
structure and dynamics of cold water super earths the case of occluded ch4 and its outgassing
arXiv: Earth and Planetary Astrophysics, 2014Co-Authors: Amit Levi, Dimitar D Sasselov, M PodolakAbstract:We study the transport of methane in the external water envelopes surrounding water-rich super-Earths and estimate its outgassing into the atmosphere. 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 relatively low mass planets lacking a H/He atmosphere. We model the thermal and structural profile of the Planetary Crust and discuss five possible Crustal regimes. 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 dynamics of the tectonic plates are analysed. We derive overturn and resurfacing time scales as well as the melt fraction underneath spreading centers. Ice mantle dynamics is found to be important for assessing the composition of the atmosphere. We formulate the relation between the outgassing flux of methane and the tectonic mode dynamics. We give numerical estimates for the global outgassing rate of methane into the atmosphere.
Dimitar D Sasselov - One of the best experts on this subject based on the ideXlab platform.
-
structure and dynamics of cold water super earths the case of occluded ch4 and its outgassing
The Astrophysical Journal, 2014Co-Authors: Amit Levi, Dimitar D Sasselov, M PodolakAbstract: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{sub 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 lowmore » 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{sub E} planet outgassing can release 10{sup 27}-10{sup 29} molecules s{sup –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.« less
-
structure and dynamics of cold water super earths the case of occluded ch4 and its outgassing
arXiv: Earth and Planetary Astrophysics, 2014Co-Authors: Amit Levi, Dimitar D Sasselov, M PodolakAbstract:We study the transport of methane in the external water envelopes surrounding water-rich super-Earths and estimate its outgassing into the atmosphere. 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 relatively low mass planets lacking a H/He atmosphere. We model the thermal and structural profile of the Planetary Crust and discuss five possible Crustal regimes. 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 dynamics of the tectonic plates are analysed. We derive overturn and resurfacing time scales as well as the melt fraction underneath spreading centers. Ice mantle dynamics is found to be important for assessing the composition of the atmosphere. We formulate the relation between the outgassing flux of methane and the tectonic mode dynamics. We give numerical estimates for the global outgassing rate of methane into the atmosphere.
Peter I Nabelek - One of the best experts on this subject based on the ideXlab platform.
-
temperature dependent thermal diffusivity of the earth s Crust and implications for magmatism
Nature, 2009Co-Authors: Alan G Whittington, Anne M Hofmeister, Peter I NabelekAbstract:The rate of heat transfer by conduction is the dominant factor that determines the thermal evolution of Planetary Crust and lithosphere. Most thermal models of the Earth's Crust assume constant values for thermal diffusivity, owing to large experimental uncertainties in measuring this property of rocks at high temperature. Whittington et al. have used recent advances in laser-flash analysis on three different Crustal rocks types to show that thermal diffusivity strongly decreases with increasing temperature. They find thermal diffusivity to be about half that commonly assumed at mid-Crustal temperatures and therefore conclude that the hot middle and lower Crust is a much more effective thermal insulator than previously thought. They also present models of lithospheric thermal evolution during continental collision, and demonstrate that the temperature dependence of rock properties leads to a positive feedback between strain heating in shear zones and more efficient thermal insulation, removing the requirement for unusually high radiogenic heat production to achieve Crustal melting temperatures. The thermal evolution of Planetary Crust and lithosphere is governed by the rate of heat transfer by conduction, which is determined by the rock's thermal diffusivity, usually assumed to remain constant. Alan Whittington and colleagues show that thermal diffusivity in fact decreases strongly with increasing temperature, concluding that the hot middle and lower Crust is a much more effective thermal insulator than previously thought; this removes the requirement for unusually high radiogenic heat production to achieve Crustal melting temperatures. The thermal evolution of Planetary Crust and lithosphere is largely governed by the rate of heat transfer by conduction1,2,3. The governing physical properties are thermal diffusivity (κ) and conductivity (k = κρCP), where ρ denotes density and CP denotes specific heat capacity at constant pressure. Although for Crustal rocks both κ and k decrease above ambient temperature4,5, most thermal models of the Earth’s lithosphere assume constant values for κ (∼1 mm2 s-1) and/or k (∼3 to 5 W m-1 K-1)6,7 owing to the large experimental uncertainties associated with conventional contact methods at high temperatures. Recent advances in laser-flash analysis8,9 permit accurate (±2 per cent) measurements on minerals and rocks to geologically relevant temperatures10. Here we provide data from laser-flash analysis for three different Crustal rock types, showing that κ strongly decreases from 1.5–2.5 mm2 s-1 at ambient conditions, approaching 0.5 mm2 s-1 at mid-Crustal temperatures. The latter value is approximately half that commonly assumed, and hot middle to lower Crust is therefore a much more effective thermal insulator than previously thought. Above the quartz α–β phase transition, Crustal κ is nearly independent of temperature, and similar to that of mantle materials11. Calculated values of k indicate that its negative dependence on temperature is smaller than that of κ, owing to the increase of CP with increasing temperature, but k also diminishes by 50 per cent from the surface to the quartz α–β transition. We present models of lithospheric thermal evolution during continental collision and demonstrate that the temperature dependence of κ and CP leads to positive feedback between strain heating in shear zones and more efficient thermal insulation, removing the requirement for unusually high radiogenic heat production to achieve Crustal melting temperatures. Positive feedback between heating, increased thermal insulation and partial melting is predicted to occur in many tectonic settings, and in both the Crust and the mantle, facilitating Crustal reworking and Planetary differentiation12.
Robert J Rosenbauer - One of the best experts on this subject based on the ideXlab platform.
-
differentiating biotic from abiotic methane genesis in hydrothermally active Planetary surfaces
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Camille L Jones, Jonas I Goldsmith, Robert J RosenbauerAbstract:Molecular hydrogen (H2) is derived from the hydrothermal alteration of olivine-rich Planetary Crust. Abiotic and biotic processes consume H2 to produce methane (CH4); however, the extent of either process is unknown. Here, we assess the temporal dependence and limit of abiotic CH4 related to the presence and formation of mineral catalysts during olivine hydrolysis (i.e., serpentinization) at 200 °C and 0.03 gigapascal. Results indicate that the rate of CH4 production increases to a maximum value related to magnetite catalyzation. By identifying the dynamics of CH4 production, we kinetically model how the H2 to CH4 ratio may be used to assess the origin of CH4 in deep subsurface serpentinization systems on Earth and Mars. Based on our model and available field data, low H2/CH4 ratios (less than approximately 40) indicate that life is likely present and active.