DISSOLUTION KINETICS OF SERPENTINE UNDER ICY JOVIAN SATELLITE CONDITIONS: IMPLICATIONS FOR EUROPA’S BIOSPHERE

Galileo spacecraft data collected from the Jovian moon, Europa, suggested the satellite was differentiated and composed of a metallic core underlying a silicate rock mantle that is below a liquid water ocean and capped with ice (Anderson et al., 1997, 1998). Prinn and Fegley (1981) proposed a detailed chemical model for the Jovian subnebula, suggesting the rocky mantle is enriched with magnesium in the form of hydrated silicates such as serpentine. The likely presence of a liquid water ocean suggests the temperature at the mantle-ocean interface may be warm enough to host life. Because the liquid ocean is in contact with a silicate mantle, water-rock interactions likely result in bioavailable nutrients in the ocean. It is possible that these water-rock interactions could proceed differently in the presence or absence of life, and that a biosignatures could be present in Europa’s liquid ocean that would provide surficial evidence of possible deeper life.

In order to test whether serpentinite reacted under Europan conditions will exert distinct biosignatures in the presence of organic acids or molecules, we propose a series of experiments utilizing continuously stirred batch reactors carried out under varying temperatures (65°C, 25°C, and 0°C) that are plausible for water-rock interactions on Europa. Surface area will be measured using BET surface area analysis on powered samples. Temperatures will be maintained using an ice bath and a heating bath. Input solutions will be composed of solutions containing organic and inorganic acids, adjusted to a salinity of 1 ppm based on estimates of the chemistry of the Europan ocean (Melosh, Ekholm, Showman, & Lorenz, 2004). Samples will be collected, measured for pH, filtered, acidified, and measured for cations by Atomic Absorption Spectroscopy, trace elements by Inductively Coupled Plasma- Mass spectrometry, and anions by Ion Chromatography. To determine the rate of dissolution we will use a relationship between the apparent rate, mass, and surface area. Additionally, we will determine the role of trace element biosignatures by calculating the percentage release of certain elements.