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| Paper: |
Characterizing Proterozoic Earth-like Planets in the Near Ultraviolet with HWO |
| Monograph: |
11, HWO25 Proceedings Part II: Mission Framework, Technology, and Broader Contributions |
| Page: |
137 |
| Authors: |
Amber V. Young, Giada Arney, Tyler D. Robinson, Shawn D. Domagal-Goldman, Roser Juanola-Parramon, Christopher C. Stark, Renyu Hu, Armen Tokadjian, and Mario Damiano |
| DOI: |
10.26624/XONA6638 |
| Abstract: |
Detecting biosignatures on Proterozoic Earth-like exoplanets requires sensitivity to near ultraviolet (NUV) spectral features, particularly ozone (\ce{O3}), which serves as a proxy for molecular oxygen (\ce{O2}) in atmospheres where direct detection is challenging. Using photochemical-climate modeling and retrieval simulations, we assess the observational requirements for robust \ce{O3} detection and the potential for spectral false positives from sulfur dioxide (\ce{SO2}). Our results show that \ce{O3} abundances as low as 0.1% of present atmospheric levels can be constrained to within an order of magnitude at 1 zσz confidence using three adjacent photometric bandpasses, each with a 15% width, and a short wavelength cutoff for those observations near 0.26 z\upmuzm. The self-consistent steady state atmospheric modeling results show that \ce{SO2} buildup is difficult in a habitable environment with appreciable amounts of water vapor in its atmosphere and would require volcanic outgassing rates at least two orders of magnitude above present-day Earth to reach surface abundance levels comparable to Proterozoic Earth-like abundances of \ce{O3}. Even under these high \ce{SO2} flux scenarios, \ce{SO2} remains largely unconstrained with the recommended observational configuration. These findings support the inclusion of UV coronagraph instrumentation on HWO to enable biosignature detection strategies that are sensitive to atmospheric conditions spanning key phases of Earth's geological history. |
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