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| Paper: |
Atmospheres of Rocky Exoplanets Around Active M Dwarfs: The Interplay of Atmospheric Pressure, Flare-Driven Photochemistry, and Stellar Contamination |
| Monograph: |
11, HWO25 Proceedings Part II: Mission Framework, Technology, and Broader Contributions |
| Page: |
147 |
| Authors: |
Viktor Y. D Sumida, Raissa Estrela, and Adriana Valio |
| DOI: |
10.26624/PZWG3231 |
| Abstract: |
The characterization of rocky exoplanet atmospheres faces two challenges: stellar surface activity can mimic or suppress spectral features of the planetary atmosphere, while UV variability influences atmospheric photochemistry essential for habitability or abiogenesis. In this work, we explore both aspects. On the photochemistry front, using 1D photochemical-climate simulations of TOI-700 d, we demonstrate that haze production depends on atmospheric pressure (0.5-4.0 bar), UV flares, and CHz_4z/COz_2z ratios. Moderate CHz_4z/COz_2z (∼0.1-0.3) enables UV-shielding hazes, but flares dissociate methane, reducing haze opacity by more than z90%z compared to quiescent stellar phases and exposing surfaces to near-UV radiation. Our results highlight that atmospheric pressure is not a standalone parameter but interacts dynamically with stellar UV activity and composition to establish an ‘‘optimal window" for simultaneous habitability and prebiotic chemistry: at 2-4 bar under moderate flares, remnant haze (though significantly depleted by flares) and methane sustain temperatures z>285z K, enabling extremophile survival (e.g., \textit{D. radiodurans}) while allowing sufficient surface UV flux for RNA precursor synthesis. Additionally, unocculted starspots and faculae alter transmission spectra by up to 50 ppm in the optical - mimicking the broadband slope of photochemical hazes or obscuring weak molecular bands (e.g., CHz_4z, COz_2z). This introduces spectral degeneracies: haze-like slopes from spots/faculae could be misinterpreted as atmospheric aerosols, while true molecular features may remain undetectable amid stellar contamination. Our results emphasize that disentangling planetary atmospheres around active stars requires understanding the combined effects of photochemistry and stellar spectral variability. |
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