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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2404.03031 |
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| _version_ | 1866929371480064000 |
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| author | Broussard, Wynter Schwieterman, Edward W. Ranjan, Sukrit Sousa-Silva, Clara Fateev, Alexander Reinhard, Christopher T. |
| author_facet | Broussard, Wynter Schwieterman, Edward W. Ranjan, Sukrit Sousa-Silva, Clara Fateev, Alexander Reinhard, Christopher T. |
| contents | JWST has created a new era of terrestrial exoplanet atmospheric characterization, and with it the possibility to detect potential biosignature gases like CH$_{4}$. Our interpretation of exoplanet atmospheric spectra, and the veracity of these interpretations, will be limited by our understanding of atmospheric processes and the accuracy of input modeling data. Molecular cross-sections are essential inputs to these models. The photochemistry of temperate planets depends on photolysis reactions whose rates are governed by the dissociation cross-sections of key molecules. H$_{2}$O is one such molecule; the photolysis of H$_{2}$O produces OH, a highly reactive and efficient sink for atmospheric trace gases. We investigate the photochemical effects of improved H$_{2}$O cross-sections on anoxic terrestrial planets as a function of host star spectral type (FGKM) and CH$_{4}$ surface flux. Our results show that updated H$_{2}$O cross-sections, extended to wavelengths $>$200 nm, substantially impact the predicted abundances of trace gases destroyed by OH. The differences for anoxic terrestrial planets orbiting Sun-like host stars are greatest, showing changes of up to three orders of magnitude in surface CO levels, and over an order of magnitude in surface CH$_{4}$ levels. These differences lead to observable changes in simulated planetary spectra, especially important in the context of future direct-imaging missions. In contrast, the atmospheres of planets orbiting M-dwarf stars are substantially less affected. Our results demonstrate a pressing need for refined dissociation cross-section data for H$_{2}$O, where uncertainties remain, and other key molecules, especially at mid-UV wavelengths $>$200 nm. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_03031 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The Impact of Extended H$_{2}$O Cross-Sections on Temperate Anoxic Planet Atmospheres: Implications for Spectral Characterization of Habitable Worlds Broussard, Wynter Schwieterman, Edward W. Ranjan, Sukrit Sousa-Silva, Clara Fateev, Alexander Reinhard, Christopher T. Earth and Planetary Astrophysics JWST has created a new era of terrestrial exoplanet atmospheric characterization, and with it the possibility to detect potential biosignature gases like CH$_{4}$. Our interpretation of exoplanet atmospheric spectra, and the veracity of these interpretations, will be limited by our understanding of atmospheric processes and the accuracy of input modeling data. Molecular cross-sections are essential inputs to these models. The photochemistry of temperate planets depends on photolysis reactions whose rates are governed by the dissociation cross-sections of key molecules. H$_{2}$O is one such molecule; the photolysis of H$_{2}$O produces OH, a highly reactive and efficient sink for atmospheric trace gases. We investigate the photochemical effects of improved H$_{2}$O cross-sections on anoxic terrestrial planets as a function of host star spectral type (FGKM) and CH$_{4}$ surface flux. Our results show that updated H$_{2}$O cross-sections, extended to wavelengths $>$200 nm, substantially impact the predicted abundances of trace gases destroyed by OH. The differences for anoxic terrestrial planets orbiting Sun-like host stars are greatest, showing changes of up to three orders of magnitude in surface CO levels, and over an order of magnitude in surface CH$_{4}$ levels. These differences lead to observable changes in simulated planetary spectra, especially important in the context of future direct-imaging missions. In contrast, the atmospheres of planets orbiting M-dwarf stars are substantially less affected. Our results demonstrate a pressing need for refined dissociation cross-section data for H$_{2}$O, where uncertainties remain, and other key molecules, especially at mid-UV wavelengths $>$200 nm. |
| title | The Impact of Extended H$_{2}$O Cross-Sections on Temperate Anoxic Planet Atmospheres: Implications for Spectral Characterization of Habitable Worlds |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2404.03031 |