Stable carbon and hydrogen isotopic fractionation of methane gas with gas hydrate formation with application to icy satellite condition

Abstract

Methane (CH₄) gas in plume of icy satellite is regarded as one of the candidates of signature of extra biota. However, CH₄ gas in icy satellite may have also hydrothermal origin and be affected by gas hydrate. This fact does not let CH₄ detection is sufficient for conclusion for CH₄ origin. Therefore, we consider the evaluation of the elementary process of CH₄ isotopic fractionation (δ¹³C, δD) via room experiment is important for isotopic observation of icy satellite in nearly future, and investigate the isotopic fractionation with gas hydrate formation. Results in isotopic measurement show that δ¹³C and isotopic fractionation coefficient of hydrogen isotope (ε_D) of remained gas phase become lower at higher pressure. Moreover, δ¹³C of remained gas phase also become lower at faster stirring rotation speed of hydrate formation. In this presentation, we will discuss the mechanism of these tendencies.