Water Ice Cloud Variability & Multi-Epoch Transmission Spectra of TRAPPIST-1e

By Keith Cowing
March 17, 2021
Filed under
Water Ice Cloud Variability & Multi-Epoch Transmission Spectra of TRAPPIST-1e
Maps of the column-integrated cloud water path at six different days (each separated by 60 days) from the GCM simulation with 100 mbar of CO2. The atmospheric cloud mass is greatly time-variable, with most locations experiencing both nearly cloud-free days and days with strong cloud coverage. As a result, the total cloud water path at the terminator strongly varies with time, though regions near the substellar point are perpetually cloudy.

The precise characterization of terrestrial atmospheres with the James Webb Space Telescope (JWST) is one of the utmost goals of exoplanet astronomy in the next decade.

With JWST’s impending launch, it is crucial we are well prepared to understand the subtleties of terrestrial atmospheres – particularly ones we may have not needed to consider before due to instrumentation limitations. In this work we show that patchy ice cloud variability is present in the upper atmospheres of M-dwarf terrestrial planets, particularly along the limbs. Here we test whether these variable clouds will introduce unexpected biases in the multi-epoch observations necessary to constrain atmospheric abundances.

Using 3D ExoCAM general circulation models (GCMs) of TRAPPIST-1e, we simulate five different climates with varying pCO2 to explore the strength of this variability. These models are post-processed using NASA Goddard’s Planetary Spectrum Generator (PSG) and PandExo to generate simulated observations with JWST’s NIRSpec PRISM mode at 365 different temporal outputs from each climate.

Assuming the need for 10 transits of TRAPPIST-1e to detect molecular features at great confidence, we then use CHIMERA to retrieve on several randomly selected weighted averages of our simulated observations to explore the effect of multi-epoch observations with variable cloud cover along the limb on retrieved abundances. We find that the variable spectra do not affect retrieved abundances at detectable levels for our sample of TRAPPIST-1e models.

E. M. May, J. Taylor, T. D. Komacek, M. R. Line, V. Parmentier

Comments: 9 pages, 5 figures. Accepted to ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2103.09313 [astro-ph.EP] (or arXiv:2103.09313v1 [astro-ph.EP] for this version)
Submission history
From: Erin May
[v1] Tue, 16 Mar 2021 20:46:08 UTC (5,621 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻