[U-05_30AM2] 生命-水-鉱物-大気相互作用

[U05-07] KROME化学パッケージによる太古代大気モデリング

*Danielache Sebastian¹、上野 雄一郎²、シモンチニ エウジェニオ³ (1.上智大学・理工学部・物質生命理工学科、2.東京工業大学・地球惑星専攻、3.INAF, Astrophysical Observatory of Arcetri, Italy.)

キーワード：古大気, 硫黄, 安定同位体

Sulfur isotopic fractionation has been used as a tool to understand the composition of reducing atmospheres. Our previous work (Danielache et al., 2008 and 2012) have shown that UV-light triggers a large Sulfur Mass-Independent Fractionation (S-MIF) on the SO₂ photodissociation products. However photodissociation of unshielded UV-light alone cannot reproduce the S-MIF signals reported for the Archean and Early Proterozoic (>2300 Ma) nor its large variability mainly at 2600 Ma (D33S = +11‰) (Johnston, 2011). In order to study a planetary-like chemical network capable of accounting for a sulfur cycle in reducing conditions we have introduced a high-order solver (DLSODES) administrated by the KROME (Grassi et al.,) chemistry package. The package automatically generates a set of FORTRAN subroutines with build-in rate equations and solves them with accuracy and e?ciency for sparse networks. This technique allows us to couple a detailed 4 sulfur isotopes chemistry to a 1D transport model capable of calculating the opacities influencing photochemistry and the temperature structure of an Archean atmosphere. We present preliminary results showing the ability of the code to deal with small isotopic fractionations and compare with already existing model studies of the Archean atmosphere. Danielache, S. O., et al., (2008), High-precision spectroscopy of 32S, 33S, and 34S sulfur dioxide: Ultraviolet absorption cross sections and isotope effects, J. Geophys. Res., 113(D17), D17314, Danielache, S. O., et al., (2012), Photoabsorption cross-section measurements of 32S, 33S, 34S, and 36S sulfur dioxide for the B1B1-X1A1 absorption band, J. Geophys. Res. Atmos., 117(D24), Johnston, D. T. (2011), Multiple sulfur isotopes and the evolution of Earth's surface sulfur cycle, Earth Science Review., 106(1-2), 161-183.Grassi T., et al., (2014), KROME - a package to embed chemistry in astrophysical simulations, Monthly Notices of the Royal Astronomical Society., DOI: 10.1093/mnras/stu114 (arXiv:1311.1070 [astro-ph.GA]).