Extrasolar Planets

Detection Of An Atmosphere On A Rocky Exoplanet

By Keith Cowing
astro-ph.EP
March 10, 2021
Filed under
Detection Of An Atmosphere On A Rocky Exoplanet
The transmission spectrum of GJ 1132 b is consistent with a predominantly H2 atmosphere augmented by an aerosol and ∼0.5% each of CH4 and HCN, the latter being an indicator of photochemistry. A few percent of a spectrally inactive species, such as N2, could be present, but the total amount of spectral modulation shows the atmosphere remains H2-dominated with a low mean molecular weight. This composition is consistent with mantle outgassing. The transmission spectrum data shown here are given in the Appendix.

We report the detection of an atmosphere on a rocky exoplanet, GJ 1132 b, which is similar to Earth in terms of size and density.

The atmospheric transmission spectrum was detected using Hubble WFC3 measurements and shows spectral signatures of aerosol scattering, HCN, and CH4 in a low mean molecular weight atmosphere. We model the atmospheric loss process and conclude that GJ 1132 b likely lost the original H/He envelope, suggesting that the atmosphere that we detect has been reestablished.

We explore the possibility of H2 mantle degassing, previously identified as a possibility for this planet by theoretical studies, and find that outgassing from ultrareduced magma could produce the observed atmosphere. In this way we use the observed exoplanet transmission spectrum to gain insights into magma composition for a terrestrial planet.

The detection of an atmosphere on this rocky planet raises the possibility that the numerous powerfully irradiated Super-Earth planets, believed to be the evaporated cores of Sub-Neptunes, may, under favorable circumstances, host detectable atmospheres.

Mark R. Swain, Raissa Estrela, Gael M. Roudier, Christophe Sotin, Paul Rimmer, Adriana Valio, Robert West, Kyle Pearson, Noah Huber-Feely, Robert T. Zellem

Comments: 22 pages, 12 figures, accepted for publication in Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2103.05657 [astro-ph.EP] (or arXiv:2103.05657v1 [astro-ph.EP] for this version)
Submission history
From: Raissa Estrela
[v1] Tue, 9 Mar 2021 19:00:21 UTC (3,544 KB)
https://arxiv.org/abs/2103.05657
Astrobiology

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