General Circulation Model Constraints on the Detectability of the CO2-CH4 Biosignature Pair on TRAPPIST-1e with JWST
Abstract
Terrestrial exoplanets such as TRAPPIST-1e will be observed in a new capacity with the JWST/Near Infrared Spectrograph (NIRSpec), which is expected to be able to detect CO2, CH4, and O2 signals, if present, with multiple coadded transit observations. The CO2-CH4 pair in particular is theorized to be a potential biosignature when inferred to be in chemical disequilibrium. Here, we simulate TRAPPIST-1e's atmosphere using the ExoCAM general circulation model, assuming an optimistic haze-free, tidally locked planet with an aquaplanet surface, with varying atmospheric compositions from 10-4 bar to 1 bar of partial CO2 pressure with 1 bar of background N2. We investigate cases both with and without a modern Earth-like CH4 mixing ratio to examine the effect of CO2 and CH4 on the transmission spectrum and climate state of the planet. We demonstrate that in the optimistic haze-free cloudy case, H2O, CO2, and CH4 could all be detectable in less than 50 transits within an atmosphere of 1 bar N2 and 10 mbar CO2 during JWST's lifespan with NIRSpec as long as the noise floor is ≲10 ppm. We find that in these optimistic cases, JWST may be able to detect potential biosignature pairs such as CO2-CH4 in TRAPPIST-1e's atmosphere across a variety of atmospheric CO2 content, and that temporal climate variability does not significantly affect spectral feature variability for NIRSpec PRISM.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2023
- DOI:
- 10.3847/2041-8213/acaa3f
- arXiv:
- arXiv:2212.05052
- Bibcode:
- 2023ApJ...942L...4R
- Keywords:
-
- Exoplanet atmospheres;
- Exoplanet atmospheric composition;
- Exoplanet atmospheric variability;
- Biosignatures;
- Exoplanets;
- Habitable planets;
- Extrasolar rocky planets;
- 487;
- 2021;
- 2020;
- 2018;
- 498;
- 695;
- 511;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 11 pages, 4 figures, 1 table, accepted for publication in ApJL