Biosignatures & Paleobiology

The Role of Atmospheric Exchange in False-Positive Biosignature Detection

By Keith Cowing
June 1, 2022
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The Role of Atmospheric Exchange in False-Positive Biosignature Detection
Top Panel: Synthetic relative transit depth spectra of an atmosphere with an O TOA flux of 1 × 1010 molecules/cm2/s and a CH4 surface flux of 6 × 1010 molecules/cm2/s. A potentially detectable CH4 signal is simulated at 2.33 µm. Bottom Panel: The corresponding model transmission spectrum with the top four absorbers at 2.33 µm highlighted.

Saturn’s Moon Titan receives volatiles into the top of its atmosphere-including atomic oxygen-sourced from cryovolcanoes on Enceladus.

Similar types of atmosphere exchange from one body to another, such as O2 and O3 sourced from TRAPPIST-1 d, could be introduced into the upper atmosphere of TRAPPIST-1 e and might be interpreted as biosignatures.

We simulate this potential false-positive for life on TRAPPIST-1 e, by applying an external influx of water and oxygen into the top of the atmosphere using a coupled 1-D photochemical-climate model (Atmos), to predict atmospheric composition. In addition, synthetic spectral observations are produced using the Planetary Spectrum Generator for the James Webb Space Telescope, Origins Space Telescope, Habitable Exoplanet Observatory and Large Ultra-violet/Optical/Infrared Surveyor to test the detectability of abiotic-generated O2 and O3 in the presence of abiotic and biotic surface fluxes of CH4.

We determine that the incoming flux of material needed to trigger detection of abiotic O2/O3 by any of these observatories is more than two orders of magnitude (1E12 molecules/cm2/s) above what is physically plausible.

Ryan C. Felton, Sandra T. Bastelberger, Kathleen E. Mandt, Adrienn Luspay-Kuti, Thomas J. Fauchez, Shawn D. Domagal-Goldman

Comments: 23 pages, 5 figures. An edited version of this paper was published by AGU. Copyright (2022) American Geophysical Union
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2206.00028 [astro-ph.EP] (or arXiv:2206.00028v1 [astro-ph.EP] for this version)
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Journal reference: JGR Planets Volume 127, Issue 3, March 2022
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Submission history
From: Ryan Felton
[v1] Tue, 31 May 2022 18:01:52 UTC (928 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) 🖖🏻