The diagnostic power of surface heat flow measurements at Europa

Abstract

Identifying ocean-bearing moons and characterizing the physical properties of their icy shells are critical investigations for the exploration of the outer solar system, with important implications for the geophysical evolution and potential habitability of the moons. However, the measurements needed to detect an ocean and constrain ice shell thickness can be challenging to obtain with remote sensing data collected from spacecraft, particularly through flybys. Recent work has shown that surface heat flow in an ocean-bearing moon may be sufficiently different from that of a frozen moon that measurements of surface heat flow could aid in ocean detection. Here, we move a step beyond previous work to investigate the extent to which measurements of surface heat flow can be used to constrain the ice shell thickness of a known ocean moon. We begin with a case study of Jupiter's moon, Europa, for which there is remote sensing data that can facilitate the investigation. We explore the behavior of a conductive ice shell with an Andrade rheology, compute location-dependent tidal heating rather than taking a global average, and utilize spacecraft measurements to account for spatially-variable surface temperatures. We also make the assumption that the ice shell is thermally stable over the timescales of human exploration. We find that patterns of surface heat flow can provide constraints on the thickness of an ice shell, and the relative contributions of basal heating and tidal heating, provided that the surface temperature is well-characterized. Hence, maps of surface temperature and heat flow from future missions would be valuable for detecting oceans and characterizing the physical properties of ice shells as well as preparing for sub-surface access missions for which knowledge of the ice shell environment is critical.