The Impact of Variable Cloud Cover on Multi-Epoch Transmission Observations of Terrestrial Exoplanet Atmospheres.

The upcoming launch of JWST brings with it an excitement to finally have the precision necessary to begin to observe and characterize the atmospheres of true terrestrial planets via transmission spectroscopy. Previous studies of the viability of this technique have assumed cloud-free or constant-cloud-deck atmospheres to determine the number of transits necessary to tease out potential biosignature gases. In this work, we present a look at the variability of clouds on a tidally locked TRAPPIST-1e for several atmospheric compositions. Using the ExoCAM GCM post-processed through NASA Goddard’s Planetary Spectrum Generator, we present limb-averaged spectra showing temporal variability on the timescale of days. By randomly selecting temporal outputs and added simulated JWST noise using PandExo to simulate these multi-epoch observations, we recreate the effect of this temporal variability on planned observations of TRAPPIST-1e and how it may impact our ability to measure the atmospheres of these nearby terrestrial planets.