A thermodynamic model of high temperature lava vaporization on Io

Schaefer, Laura; Fegley, B.

doi:10.1016/j.icarus.2003.08.023

Cited by 138 publications

(129 citation statements)

References 88 publications

(155 reference statements)

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“…The MAGMA code, which is a robust and rapid mass-balance, mass action algorithm, is described and validated against experimental studies in Fegley & Cameron (1987) and Schaefer & Fegley (2004a). The MAGMA code considers the elements Na, K, Fe, Mg, Si, Ti, Ca, Al, and O and their compounds.…”

Section: Methodsmentioning

confidence: 99%

Chemistry of Silicate Atmospheres of Evaporating Super-Earths

Schaefer

Fegley

2009

ApJ

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We model the formation of silicate atmospheres on hot volatile-free super-Earths. Our calculations assume that all volatile elements such as H, C, N, S, and Cl have been lost from the planet. We find that the atmospheres are composed primarily of Na, O 2 , O, and SiO gas, in order of decreasing abundance. The atmospheric composition may be altered by fractional vaporization, cloud condensation, photoionization, and reaction with any residual volatile elements remaining in the atmosphere. Cloud condensation reduces the abundance of all elements in the atmosphere except Na and K. We speculate that large Na and K clouds such as those observed around Mercury and Io may surround hot super-Earths. These clouds would occult much larger fractions of the parent star than a closely bound atmosphere, and may be observable through currently available methods.

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Section: Methodsmentioning

confidence: 99%

Chemistry of Silicate Atmospheres of Evaporating Super-Earths

Schaefer

Fegley

2009

ApJ

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235

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“…The vapour pressures of the species evaporating from the meteoroid were calculated using the MAGMA chemical equilibrium code (Fegley and Cameron, 1987;Schaefer and Fegley, 2004;Schaefer and Fegley, 2005). The code is robust and fast, and exhibits good agreement with experimental data for a wide range of temperatures and silicate melt compositions.…”

Section: Vapour -Molten Meteoroid Thermodynamic Equilibriummentioning

confidence: 99%

A chemical model of meteoric ablation

et al. 2008

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Abstract. Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD) is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K) through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides), and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca + in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si) have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. DiffusionCorrespondence to: J. M. C. Plane (j.m.c.plane@leeds.ac.uk) of the most volatile elements (Na and K) does not appear to be rate-limiting except in the fastest meteoroids. Nonthermal sputtering causes ∼35% mass loss from the fastest (∼60-70 km s −1 ) and smallest (10 −17 -10 −13 g) meteoroids, but makes a minor contribution to the overall ablation rate.

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“…Vapour pressures are calculated from the multicomponent gas-melt chemical equilibrium code MAGMA (Fegley & Cameron 1987;Schaefer & Fegley Jr 2004a). MAGMA was validated by (Schaefer & Fegley Jr 2004b) by successful modelling of the residual compositions resulting from 7 experiments of partial evaporation into a vacuum of synthetic CI-like and CAIs-like materials 2 (Hashimoto 1983;Wang et al 2001) and of lunar aluminiferous basalt (Markova et al 1986) (Richter et al 2002). A potential problem is that much of the thermodynamic data in MAGMA has to be extrapolated to T > 2000 K from measurements below 1700 K.…”

Section: Introductionmentioning

confidence: 99%