Ocean dynamics and tracer transport over the south pole geysers of Enceladus

Abstract

ABSTRACTOver the south pole of Enceladus, an icy moon of Saturn, geysers eject water into space in a striped pattern, making Enceladus one of the most attractive destinations in the search for extraterrestrial life. We explore the ocean dynamics and tracer/heat transport associated with geysers as a function of the assumed salinity of the ocean and various core-shell heat partitions and bottom heating patterns. We find that, even if heating is concentrated into a narrow band on the seafloor directly beneath the south pole, the warm fluid becomes quickly mixed with its surroundings due to baroclinic instability. The warming signal beneath the ice is diffuse and insufficient to prevent the geyser from freezing over. Instead, if heating is assumed to be local to the geyser (either generated in the ice due to tidal dissipation or friction or generated in the ocean as water flushes in/out of the geyser slot under tidal forcing), geyser can be sustained. In this case, the upper ocean beneath the ice becomes stably stratified creating a barrier to vertical communication, leading to transit time-scales from the core to the ice shell of hundreds of years in contrast to purported transit time-scales of weeks to months.