[MIS07-P17] New sulfur isotopes 1-D photochemical model for revealing early earth's atmosphere
Keywords:Earth's Early atmosphere, Sulfur isotope
Constraining the atmospheric composition of planets is essential to understanding habitability. However, the chemical composition of the early Earth's atmosphere is poorly understood. Here, mass-independent fractionation of sulfur isotopes (MIF-S) in pre-2.4 Ga sedimentary rocks provide a hint of atmospheric composition at that time. For the early Earth, it is believed that partial pressure of O2 was very low and atmosphere was reducing. Recently, our sulfur dioxide (SO2) photochemical experiments under carbon monoxide (CO) atmosphere reproduced the Δ36S/Δ33S slope from the Archean (~−1), which is the most basic character of Archean MIF-S (Endo et al. 2016). Moreover, it was found that the MIF-S trend depends on total pressure, indicating that MIF-S is sensitive to absorption spectral shape of SO2 via SO2’s own UV absorption (Endo et al. 2019). We synthesized SO2 isotopologues absorption spectra which reproduce the MIF-S of photochemical experiments (Endo et al. 2019). Therefore, we can predict MIF-S produced in various atmospheric compositions using the SO2 isotopologues absorption spectra and irradiative UV spectra, and the resulting MIF-S depends on altitude. Here, we develop a 1-D (vertical) photochemical model including 4 sulfur isotopes (32S, 33S, 34S, and 36S) and very high resolution SO2 absorption spectra (~0.0004 nm). This new model is based on previous models including sulfur isotopes and low wavelength resolution SO2 absorption spectra (Claire et al. 2014; Izon et al. 2017). We will present preliminary results and discuss the meaning of MIF-S in Early Earth rocks and modern atmospheric sulfates, if possible, Martian meteorites.