Title: Regimes of hydrothermal plumes on Icy Ocean Worlds

Abstract: The icy ocean worlds (e.g., Enceladus, Europa) are promising astrobiological targets since they potentially have regions with active water-rock interaction and hydrothermal activity at present-day. However, these habitable environments are typically overlain by a thick (>10 km) ocean and ice shell. Thus, to interpret surface observations, we need to understand the efficiency and the timescale over which fluids and particles get transported from the ocean-- core to the surface. I will present some of my ongoing work to address these challenging using high-resolution (~ 40-80m grid resolution) fluid dynamical simulations to analyze hydrothermal plume dynamics in an icy ocean world context. These results significantly expand upon previous work by Goodman et al. (2004, 2012) by considering a larger range of: (i) hydrothermal heat fluxes (in particular lower heat fluxes < 100 W/m 2 - consistent with estimates from tidal dissipation models), (ii) planetary rotation rates, and (iii) plume latitudes (polar to equatorial). We find that, in contrast to typical terrestrial hydrothermal plumes, baroclinic eddies play a critical role in the rotational plume dynamics in a deep icy ocean worlds in presence of minimal ocean stratification. The eddies efficiently transport heat laterally away from the vent location on a timescale faster than plume rise timescale. Consequently, a buoyant rotating plume rises much more slowly compared to a non-rotating plume. Using scaling results calibrated with the simulations, we find that the transit time across Enceladus's ocean for highest 1% of hydrothermal plume particles is at least ~ 100 yrs, if not significantly longer. This timescale significantly exceeds the months-to-a-few-years estimate based on a core hydrothermal activity model for silica nanoparticles observed in Enceladus’s plume. These results have significant implications for interpreting the measured geyser fluid compositions (e.g., methane, hydrogen, CO 2 ) in the context of planetary habitability and ocean dynamics.

Astro Colloquium and 'coffee & cookies' department gathering (3:45-4:00pm)

Please click the link to join virtually: https://psu.zoom.us/j/92637070419