Downward Oxidant Transport Through Europa's Ice Shell by Density‐Driven Brine Percolation

Abstract

Abstract Jupiter's moon Europa is thought to have an ocean beneath its ice shell and the habitability of the internal ocean depends on the availability of redox gradients. Downward transport of radiolytic materials produced at the surface through the ice shell sets the flux of oxidants into the ocean. Here, we propose that oxidants are transported through the ice shell by the drainage of near‐surface brines formed concurrently with chaotic terrains. We estimate that Europa's porous regolith contains 3.7 × 10 14 to 5.6 × 10 18 mol (1.2 × 10 13 − 1.8 × 10 17 kg) of trapped O 2 . Simulations of coupled melt‐migration and eutectic phase behavior show that brines drain before they refreeze, delivering ∼85% of the surface oxidants to the ocean on timescales of 2 × 10 4 years. From the distribution of chaotic terrains and from Europa's surface age we estimate that brine drainage could deliver O 2 to the ocean at rates of 2.0 × 10 6 to 1.3 × 10 10 mol/yr (0.002−13.2 kg/s).

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