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Detectability of Biosignature Gases in the Mid-infrared for Secondary Eclipse Spectra

Presentation #108.09 in the session Astrobiology and Origins of Life (Oral Presentation)

Published onOct 23, 2023
Detectability of Biosignature Gases in the Mid-infrared for Secondary Eclipse Spectra

For the foreseeable future, atmospheric characterization with the James Webb Space Telescope (JWST) will provide our primary window into understanding the nature of exoplanets. JWST is the only near-term space-based telescope that will observe exoplanets in the mid-infrared (mid-IR) wavelengths that are informative for atmospheric characterization and biosignature detection. Follow-on observatories like the Origins Space Telescope will provide immense scientific value, but at substantial cost and constrained, competitive observation time. Smaller space-based telescopes have the potential to provide valuable science complementary to larger observatories.

We have investigated the utility of small-aperture telescopes compared to larger telescopes via simulated exoplanet spectra. We modified model spectra based on expected measurement constraints (resolving power, number of eclipses, and aperture size) and used atmospheric retrievals to analyze the temperature, pressure, and composition information that can be extracted from the modified spectra. We have modeled atmospheric emission spectra for a TRAPPIST-1e-like planet orbiting an M-dwarf star and modified these simulated spectra for different signal-to-noise ratios and resolving powers. We then used atmospheric retrievals to analyze these modified spectra and assess the minimum observation parameters to determine habitability (e.g., from temperature and water abundance) and detectability of biosignatures (e.g., O3 and CH4).

For a TRAPPIST-1e-like planet, we find that surface temperature is one of the few model parameters that can be constrained with a 2m aperture, though with a very large number of eclipses (N = 1000). CO2 and O3 can be constrained for large apertures and many eclipses, whereas we are able to estimate lower and upper bounds on H2O and CH4 respectively. We find the 5-10 μm range to be consequential to constraining H2O and CH4, and that minimizing detector noise is critical to enabling useful observations of terrestrial exoplanets for telescopes of aperture sizes smaller than approximately 3m.

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