10:45 AM - 11:00 AM
[MIS14-01] Internal heating of icy ocean worlds
Keywords:Icy satellites, Tidal heating
Surface temperatures of outer solar system bodies are very low (i.e., ~100 K), and the surface of the most solid bodies are covered by ice mainly composed of water. Despite its low temperature, some of such icy bodies are “aqua planets”; they possess subsurface oceans. It can be said that one of the major research subjects in Aqua planetology is to understand how such oceans are maintained.
In addition to the decay of radiogenic isotopes only slightly contained in rocks, tidal heating is considered as an important heat source maintaining subsurface ocean in satellites of giant planets. Recent theoretical studies quantifying the amount of heat produced in internal solid and liquid layers enable us to calculate the total amount as well as the spatial pattern of heating for a given internal structural model and orbital property. Nevertheless, little is known about the total amount and the spatial pattern of heating on actual satellites because of large uncertainties in their interior structures.
In this study, we calculate the total amount and the spatial pattern of tidal heating in several icy satellites, such as the Jovial icy satellite Europa, the Saturnian icy satellite Enceladus, the Neptunian satellite Triton, under a wide variety of parameter conditions using previously-reported theoretical models. We confirm that Europa and Enceladus are mainly heated by eccentricity-type, while Triton is heated by inclination-type tides, and that the total amount of heat due to the former increases while the latter decreases with increasing ocean thickness. We find that a large increase in the heating rate due to tidal resonance is unlikely to occur for Enceladus. We also find that the spatial pattern of solid tides is not sensitive to the interior structure while that of liquid tides is; the latter relatively strongly depends on the ocean thickness and the drag coefficient. This result implies that the main heating mechanism and/or the mean ocean thickness can be constrained based on the shape of the ice shell.
In addition to the decay of radiogenic isotopes only slightly contained in rocks, tidal heating is considered as an important heat source maintaining subsurface ocean in satellites of giant planets. Recent theoretical studies quantifying the amount of heat produced in internal solid and liquid layers enable us to calculate the total amount as well as the spatial pattern of heating for a given internal structural model and orbital property. Nevertheless, little is known about the total amount and the spatial pattern of heating on actual satellites because of large uncertainties in their interior structures.
In this study, we calculate the total amount and the spatial pattern of tidal heating in several icy satellites, such as the Jovial icy satellite Europa, the Saturnian icy satellite Enceladus, the Neptunian satellite Triton, under a wide variety of parameter conditions using previously-reported theoretical models. We confirm that Europa and Enceladus are mainly heated by eccentricity-type, while Triton is heated by inclination-type tides, and that the total amount of heat due to the former increases while the latter decreases with increasing ocean thickness. We find that a large increase in the heating rate due to tidal resonance is unlikely to occur for Enceladus. We also find that the spatial pattern of solid tides is not sensitive to the interior structure while that of liquid tides is; the latter relatively strongly depends on the ocean thickness and the drag coefficient. This result implies that the main heating mechanism and/or the mean ocean thickness can be constrained based on the shape of the ice shell.