Biosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One Flare
Many past studies have predicted the steady-state production and maintenance of abiotic O _2 and O _3 in the atmospheres of CO _2 -rich terrestrial planets orbiting M dwarf stars. However, the time-dependent responses of these planetary atmospheres to flare events—and the possible temporary producti...
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2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acebec |
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| author | Arturo Miranda-Rosete Antígona Segura Edward W. Schwieterman |
| author_facet | Arturo Miranda-Rosete Antígona Segura Edward W. Schwieterman |
| author_sort | Arturo Miranda-Rosete |
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| description | Many past studies have predicted the steady-state production and maintenance of abiotic O _2 and O _3 in the atmospheres of CO _2 -rich terrestrial planets orbiting M dwarf stars. However, the time-dependent responses of these planetary atmospheres to flare events—and the possible temporary production or enhancement of false-positive biosignatures therein—has been comparatively less well studied. Most past works that have modeled the photochemical response to flares have assumed abundant free oxygen, like that of the modern or Proterozoic Earth. Here we examine in detail the photochemical impact of the UV emitted by a single flare on abiotic O _2 /O _3 production in prebiotic, CO _2 -dominated atmospheres of M dwarf planets with CO _2 levels ranging from 3% to 80% of 1 bar. We find that a single flare generally destroys O _2 and O _3 over short timescales while modestly enhancing their column densities over intermediate timescales. We simulate the spectral observables of both the steady-state atmosphere and time-dependent spectral response over the flare window for both emitted and transmitted light spectra. Over the course of the flare, the O _3 UV Hartley band is decreased by a maximum of 47 ppm. In both emitted and transmitted light spectra, the 9.65 μ m O _3 band is hidden by the overlapping 9.4 μ m CO _2 band for all scenarios considered. Overall, we find that the possible enhancements of abiotic O _3 due to a single flare are small compared to O _3 ’s sensitivity to other parameters such as CO _2 and H _2 O abundances or the availability of reducing gases such as H _2 . |
| format | Article |
| id | doaj-art-7d799acd9296450c8857fef5965e2fe6 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-7d799acd9296450c8857fef5965e2fe62025-08-20T03:16:17ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198913410.3847/1538-4357/acebecBiosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One FlareArturo Miranda-Rosete0https://orcid.org/0000-0002-2857-0131Antígona Segura1https://orcid.org/0000-0002-2240-2452Edward W. Schwieterman2https://orcid.org/0000-0002-2949-2163Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México , Mexico ; arturo.miranda@correo.nucleares.unam.mxInstituto de Ciencias Nucleares, Universidad Nacional Autónoma de México , Mexico ; arturo.miranda@correo.nucleares.unam.mx; NASA Nexus for Exoplanet System Science , Virtual Planetary Laboratory Team, Seattle, WA, USANASA Nexus for Exoplanet System Science , Virtual Planetary Laboratory Team, Seattle, WA, USA; Department of Earth and Planetary Sciences, University of California , Riverside, CA, USA; Blue Marble Space Institute of Science , Seattle, WA, USAMany past studies have predicted the steady-state production and maintenance of abiotic O _2 and O _3 in the atmospheres of CO _2 -rich terrestrial planets orbiting M dwarf stars. However, the time-dependent responses of these planetary atmospheres to flare events—and the possible temporary production or enhancement of false-positive biosignatures therein—has been comparatively less well studied. Most past works that have modeled the photochemical response to flares have assumed abundant free oxygen, like that of the modern or Proterozoic Earth. Here we examine in detail the photochemical impact of the UV emitted by a single flare on abiotic O _2 /O _3 production in prebiotic, CO _2 -dominated atmospheres of M dwarf planets with CO _2 levels ranging from 3% to 80% of 1 bar. We find that a single flare generally destroys O _2 and O _3 over short timescales while modestly enhancing their column densities over intermediate timescales. We simulate the spectral observables of both the steady-state atmosphere and time-dependent spectral response over the flare window for both emitted and transmitted light spectra. Over the course of the flare, the O _3 UV Hartley band is decreased by a maximum of 47 ppm. In both emitted and transmitted light spectra, the 9.65 μ m O _3 band is hidden by the overlapping 9.4 μ m CO _2 band for all scenarios considered. Overall, we find that the possible enhancements of abiotic O _3 due to a single flare are small compared to O _3 ’s sensitivity to other parameters such as CO _2 and H _2 O abundances or the availability of reducing gases such as H _2 .https://doi.org/10.3847/1538-4357/acebecM dwarf starsStellar flaresExoplanet atmospheresBiosignaturesExoplanetsHabitable planets |
| spellingShingle | Arturo Miranda-Rosete Antígona Segura Edward W. Schwieterman Biosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One Flare The Astrophysical Journal M dwarf stars Stellar flares Exoplanet atmospheres Biosignatures Exoplanets Habitable planets |
| title | Biosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One Flare |
| title_full | Biosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One Flare |
| title_fullStr | Biosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One Flare |
| title_full_unstemmed | Biosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One Flare |
| title_short | Biosignature False Positives in Potentially Habitable Planets around M Dwarfs: The Effect of UV Radiation from One Flare |
| title_sort | biosignature false positives in potentially habitable planets around m dwarfs the effect of uv radiation from one flare |
| topic | M dwarf stars Stellar flares Exoplanet atmospheres Biosignatures Exoplanets Habitable planets |
| url | https://doi.org/10.3847/1538-4357/acebec |
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