Exploring the Interior Structure and Mode of Tidal Heating in Enceladus

TL;DR

This paper develops a statistical framework to analyze Enceladus's interior structure and tidal heating, emphasizing how geodetic measurements can distinguish between shell and core dissipation, crucial for understanding its habitability.

Contribution

It introduces a method to constrain Enceladus's interior and tidal dissipation distribution using measurements of libration, shape, heat flux, gravity, and mass, highlighting the importance of Love numbers.

Findings

Measuring k2 constrains total tidal energy dissipation.

H2 and l2 measurements reveal dissipation locations in shell or core.

Future geodetic data can differentiate between heating scenarios.

Abstract

Enceladus is among the most intriguing bodies in the solar system due to its astrobiological potential. Determining the extent and duration of habitability (i.e., sustained habitability) requires characterizing the interior properties and the level and distribution of tidal heating in Enceladus. Inferring the intensity of geophysical activity in the core has direct implications for the potential hydrothermal activity and supply of chemical species important for habitability to the ocean. We build a statistical framework to constrain the interior using estimates of libration, shape, heat flux, gravity, and total mass. We use this framework to examine the extent that geodetic measurements can improve our understanding of the interior structure, with an emphasis on partitioning of dissipation between the shell and the core. We quantify plausible ranges of gravitational (k2) and displacement (h2, l2) tidal Love numbers consistent with existing observations. We demonstrate that measuring k2 alone can only constrain the total tidally dissipated energy, but not its radial distribution. However, measuring the amplitude and phase of h2 or l2 facilitates determining the extent of tidal dissipation in the shell and the core. We provide the precisions required for measuring k2, h2, and l2 that enable distinguishing between the main tidal heating scenarios, i.e., in the shell versus the core. We also explore the effect of the structural heterogeneities of the shell on the tidal response. Lastly, we evaluate the efficacy of future geodetic measurements to constrain key interior properties essential to understand the present-day (instantaneous) and long-term (sustained) habitability at Enceladus.