PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

ABSTRACT GJ 1132b is a nearby Earth-sized exoplanet transiting an M dwarf, and is among the most highly characterizable small exoplanets currently known. In this paper, we study the interaction of a magma ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more...

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Bibliographic Details
Published in:The Astrophysical journal 2016-10, Vol.829 (2), p.63
Main Authors: Schaefer, Laura, Wordsworth, Robin D., Berta-Thompson, Zachory, Sasselov, Dimitar
Format: Article
Language:English
Subjects:
Astrophysics
Atmosphere
Atmospheres
Atmospheric composition
Atmospheric models
Carbon dioxide
Carbon dioxide atmospheric concentrations
Computer simulation
Dissociation
Extrasolar planets
Hydrogen
Magma
Ocean models
Oceans
planet-star interactions
planets and satellites: atmospheres
planets and satellites: composition
planets and satellites: individual (GJ 1132b)
Steam
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Summary:ABSTRACT GJ 1132b is a nearby Earth-sized exoplanet transiting an M dwarf, and is among the most highly characterizable small exoplanets currently known. In this paper, we study the interaction of a magma ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the amount of O2 that can build up in the atmosphere as a result of hydrogen dissociation and loss. We find that the magma ocean absorbs at most ∼10% of the O2 produced, whereas more than 90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132b from our simulations is a tenuous atmosphere dominated by O2, though, for very large initial water abundances, atmospheres with several thousands of bars of O2 are possible. A substantial steam envelope would indicate either the existence of an earlier H2 envelope or low XUV flux over the system's lifetime. A steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132b. Further modeling is needed to study the evolution of CO2 or N2-rich atmospheres on GJ 1132b.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/829/2/63