Chemical Fractionation Modeling of Plumes Indicates a Gas-rich, Moderately Alkaline Enceladus Ocean

Abstract Enceladus harbors an ocean beneath its ice crust that erupts spectacular plumes from fissures at the south pole. The plume composition was measured by Cassini spacecraft, and provides evidence for ocean’s gas content, salinity, pH, potential life. Understanding is complicated physicochemical processes alter during eruption, such as water vapor condensation in icy exsolution surface. We developed a model includes key fractionation processes, particular exsolution, which has not been previously considered. Our predicts moderately alkaline (pH 7.95–9.05), gas-rich (?10 ?5 –10 ?3 molal) with high concentrations of ammonium ions (10 ?2 ?1 molal). derived dissolved are higher than recent studies because we account depletes gases compared to ocean, our conserves mass flow rates between eruption tiger stripe fissures. find carbon dioxide hydrogen could provide sufficient chemical energy oceanic life form hydrogenotrophic methanogens. Carbon 10 molal indicate more Earth-like pH ?8.5–13.5 previous studies. inferred bulk total inorganic consistent cometary levels. This corroborates deuterium-hydrogen (D/H) ratios formed comet-like planetesimals. results suggest inherited volatile building blocks.