Chemistry of Silicate Atmospheres of Evaporating Super-Earths

Abstract

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, O2, 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.

18 pages, 3 figures, 1 table, submitted to ApJ Letters

References in corpus (5)

• Sodium Absorption From the Exoplanetary Atmosphere of HD189733b Detected in the Optical Transmission Spectrum
• The Atmospheric Signatures of Super-Earths: How to Distinguish Between Hydrogen-Rich and Hydrogen-Poor Atmospheres
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Cited by in corpus (2)

• Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths
• Dusty tails of evaporating exoplanets. I. Constraints on the dust composition