![\"Ultraviolet-Driven](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/06\/Ultraviolet.png\")
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\n Comparison of input SEDs used in this study and molecular photoabsorption cross sections relevant to Archean-analog photochemistry. The horizontal bars indicate the FUV and NUV wavelength intervals used to compute the stellar FUV\/NUV ratios in Figures 5 and 7. Top: Top-of-atmosphere (ToA) stellar energy fluxes at TRAPPIST-1 e from 120\u2013350 nm for five SEDs: Peacock+2019 (P19) Median (orange) (S. Peacock et al. 2019), Mega-MUSCLES (W21) Adaptive (yellow), Mega-MUSCLES (W21) SEM (light blue) (D. J. Wilson et al. 2021), a \u201cRevised PHOENIX\u201d model (dark blue) constrained by the HST observations published in D. J. Wilson et al. (2021), and a scaled modern Sun (red) (G. Thuillier et al. 2004). All SEDs are scaled to TRAPPIST-1 e\u2019s ToA irradiance. Bottom: Representative molecular cross sections for CH4 (pink), CO2 (black), H2O (green), O2 (light blue), and O3 (dark blue) are shown, highlighting the wavelength overlap between the cross sections and the stellar UV output. Where both the flux and the cross section are large, photolysis rates increase and influence production and loss pathways throughout the atmosphere. \u2014 astro-ph.EP <\/p>\n
The ultraviolet (UV) spectrum of a host star strongly shapes the atmospheric composition and potential biosignatures of its planets. This relationship may be especially important for the planets orbiting TRAPPIST-1, an M8V star with substantially different published UV spectral energy distributions (SEDs).<\/p>\n
Using a one-dimensional photochemical model, we quantify how these SED uncertainties affect Archean Earth-like atmospheric analogs on TRAPPIST-1 e with and without biospheres. We emphasize Earth\u2019s Archean epoch because it represents a planet in transition from primarily abiotic to biotic controls on atmospheric composition.<\/p>\n
Different stellar spectra produce order-of-magnitude variations in the predicted abundances of CH4, CO, O2, and O3, thereby generating photochemical degeneracies that complicate the interpretation of potential biosignatures.<\/p>\n
For one TRAPPIST-1 UV reconstruction, a modeled atmosphere with abiotic deposition velocities and volcanic CH4 input can sustain simultaneous spectrally discernible CH4 and O3, yielding a potential false-positive disequilibrium biosignature.<\/p>\n
For all SEDs tested, surface deposition consistent with microbially-mediated CO consumption allows substantial O2 and O3 accumulation even without oxygenic photosynthesis, implying that oxygen-rich atmospheres around ultracool M dwarfs may not uniquely trace oxygenic ecosystems. Across our models, CO remains a powerful discriminator between abiotic and biotic surface boundary assumptions.<\/p>\n
Overall, we show that the abundances of co-occurring CH4, CO, and O3 can vary by orders of magnitude, depending on the assumed UV SED, creating ambiguities in interpreting atmospheric biosignatures, though observability may be challenging with current capabilities. Reducing UV spectral uncertainties is therefore essential for assessing surface-to-atmosphere interactions of temperate exoplanets around ultracool M dwarfs.<\/p>\n
Evan L. Sneed, Edward W. Schwieterman, Sarah R. Peacock, Nicholas F. Wogan, Timothy W. Lyons<\/p>\n
Comments: 23 pages, 7 figures, 1 table. Submitted to AAS Journals. Comments welcome Astrobiology, Astrogeology,<\/p>\n","protected":false},"excerpt":{"rendered":"Comparison of input SEDs used in this study and molecular photoabsorption cross sections relevant to Archean-analog photochemistry. The…\n","protected":false},"author":2,"featured_media":488478,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[10803,71490,910,49380,61,60,148631,82,2811,209937,25720,162956],"class_list":["post-488477","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-atmosphere","tag-biosignature","tag-exoplanet","tag-habitability","tag-ie","tag-ireland","tag-m-dwarf","tag-science","tag-spectroscopy","tag-terrestrial-planet","tag-trappist-1","tag-trappist-1-e"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/488477","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=488477"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/488477\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/488478"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=488477"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=488477"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=488477"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2606.05451 [astro-ph.EP] (or arXiv:2606.05451v1 [astro-ph.EP] for this version)
https:\/\/doi.org\/10.48550\/arXiv.2606.05451<\/a>
Focus to learn more
Submission history
From: Evan Sneed
[v1] Wed, 3 Jun 2026 21:15:43 UTC (697 KB)
https:\/\/arxiv.org\/abs\/2606.05451<\/a><\/p>\n