Surface‐To‐Ocean Exchange by the Sinking of Impact Generated Melt Chambers on Europa

Abstract

Many icy moons in the outer Solar System host large subsurface oceans maintained by tidal heating (Nimmo & Pappalardo, 2016), and are considered the most likely bodies in our Solar System to host habitable environments (Domagal-Goldman et al., 2016;Gaidos et al., 1999). The upcoming JUICE and Europa Clipper missions will specifically target the habitability of Jupiter's moon Europa (Grasset et al., 2013;Howell & Pappalardo, 2020). One major unknown is the source of oxidants that are necessary to generate and maintain redox gradients within its ocean (

Multiring basin formation constrains Europa’s ice shell thickness

“…In all cases, the center of the basin contains a melt pool (fig. S2B), which may cause exchange between the surface and ocean even in the case of a thick ice shell (38). Our results show that there is some trade-off between impactor size and lithospheric thickness.…”

Evolution of Impact Melt Pools on Titan

“…(b) Europa's crust is mostly made of water ice while Titan's surface may be covered by a few to tens of kilometers thick layer of thermally insulating methane clathrates. Consequently, Carnahan et al (2022) prescribe constant thermal conductivity, but we take into account the thermal dependence of ice conductivity and combine it with the Journal of Geophysical Research: Planets 10.1029/2023JE008107…”

“…We further assume that the two phases are in thermal equilibrium and that water is locked in the ice matrix and advected with it (i.e., there is no differential motion between the two phases, we call this approximation an “impermeable limit”). To capture the evolution of the thermal state as well as the phase change between the solid ice and liquid water, we use the enthalpy method (e.g., Carnahan et al., 2022; Jordan & Hesse, 2015; Katz, 2008, and Appendix ). We solve the conservation equations of mass, linear momentum, and enthalpy of the whole mixture.…”

“…To account for this effect, we follow the approach of Tobie et al. (2003) but only decrease the viscosity by ∼2 orders of magnitude in maximum (i.e., η min ∼ 10 12 Pa s, see also Carnahan et al., 2022). Similarly, for numerical reasons, we limit the maximum viscosity to ∼10 24 Pa s. We thus prescribe the mixture viscosity as follows: $$$\eta =\min \left\{\max \left[{\eta }_{\mathrm{i}}\,\mathrm{exp}\left(-{\gamma }_{\mathrm{m}}\phi \right),{\eta }_{\min }\right],{\eta }_{\max }\right\}.$$$ …”

“…In their recent paper, Carnahan et al. (2022) showed that, on Europa, impact melt pools could sink into the ice shell due to negative phase buoyancy (since water is denser than ice). In the present study, we investigate whether melt pools could similarly sink in Titan's ice shell.…”