Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System


Integrated cloud water column in kg.m−2 for aquaplanets TRAPPIST-1e (top row), 1f (middle row) and 1g (bottom row) for Charnay et al. (2013) case A (left), case B (middle) and case C (right) Archean Earth atmospheres. TRAPPIST-1g case C is missing because CO2 in the atmosphere has condensed to the night side leading to the crash of the simulation.

The TRAPPIST-1 system, consisting of an ultra-cool host star having seven known Earth-size planets will be a prime target for atmospheric characterization with JWST.

However, the detectability of atmospheric molecular species may be severely impacted by the presence of clouds and/or hazes. In this work, we perform 3-D General Circulation Model (GCM) simulations with the LMD Generic model supplemented by 1-D photochemistry simulations at the terminator with the Atmos model to simulate several possible atmospheres for TRAPPIST-1e, 1f and 1g: 1) modern Earth, 2) Archean Earth, and 3) CO2-rich atmospheres. JWST synthetic transit spectra were computed using the GSFC Planetary Spectrum Generator (PSG). We find that TRAPPIST-1e, 1f and 1g atmospheres, with clouds and/or hazes, could be detected using JWST's NIRSpec prism from the CO2 absorption line at 4.3 um in less than 15 transits at 3 sigma or less than 35 transits at 5 sigma.

However, our analysis suggests that other gases would require hundreds (or thousands) of transits to be detectable. We also find that H2O, mostly confined in the lower atmosphere, is very challenging to detect for these planets or similar systems if the planets' atmospheres are not in a moist greenhouse state. This result demonstrates that the use of GCMs, self-consistently taking into account the effect of clouds and sub-saturation, is crucial to evaluate the detectability of atmospheric molecules of interest as well as for interpreting future detections in a more global (and thus robust and relevant) approach.

Thomas J. Fauchez, Martin Turbet, Geronimo L. Villanueva, Eric T. Wolf, Giada Arney, Ravi K. Kopparapu, Andrew Lincowski, Avi Mandell, Julien de Wit, Daria Pidhorodetska, Shawn D. Domagal-Goldman, Kevin B. Stevenson
(Submitted on 19 Nov 2019)

Comments: 36 pages, 19 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1911.08596 [astro-ph.EP] (or arXiv:1911.08596v1 [astro-ph.EP] for this version)
Submission history
From: Thomas Fauchez
[v1] Tue, 19 Nov 2019 21:34:17 UTC (7,627 KB)
https://arxiv.org/abs/1911.08596
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