Tidal deformation of Ganymede: Sensitivity of Love numbers on the interior structure

Abstract

Tidal deformation of icy satellites provides crucial information on their subsurface structures. In this study, we investigate the parameter dependence of the tidal displacement and potential Love numbers (i.e., h2 and k2, respectively) of Ganymede. Our results indicate that Love numbers for Ganymede models without a subsurface ocean are not necessarily smaller than those with a subsurface ocean. The phase lag, however, depends primarily on the presence/absence of a subsurface ocean. Thus, the determination of the phase lag would be of importance to infer whether Ganymede possesses a subsurface ocean or not based only on geodetic measurements. Our results also indicate that the major control on Love numbers is the thickness of the ice shell if Ganymede possesses a subsurface ocean. This result, however, does not necessarily indicate that measurement of either of h2 or k2 alone is sufficient to estimate the shell thickness; while a thin shell leads to large h2 and k2 independent of parameters, a thick shell does not necessarily lead to small h2 and k2. We found that to reduce the uncertainty in the shell thickness, constraining k2 in addition to h2 is necessary, highlighting the importance of collaborative analyses of topography and gravity field data.

Geophysical Investigations of Habitability in Ice‐Covered Ocean Worlds

“…Other solid layers are assumed to be elastic; an infinite viscosity is assumed. Although high‐pressure ices may have low viscosities, their tidal response is nearly independent of the viscosity of high‐pressure ices if an ocean is sandwiched (Kamata et al, ). Consequently, this simplification does not affect our conclusions.…”

Tidal Response of Mars Constrained From Laboratory‐Based Viscoelastic Dissipation Models and Geophysical Data

“…While most studies focus on application of a single viscoelastic dissipation model to solar system objects: Mercury [Padovan et al, 2013], Venus [Dumoulin et al, 2017], Earth [Bellis and Holtzman, 2014;Abers et al, 2014;Agnew, 2015;Karato et al, 2015;Lau and Faul, 2019], the Moon [Nimmo et al, 2012;Efroimsky, 2012a,b;Karato, 2013;Harada et al, 2014;Williams and Boggs, 2015;Qin et al, 2016], Mars [Lognonné and Mosser, 1993;Yoder et al, 2003;Sohl et al, 2005;Zharkov and Gudkova, 2005;Bills et al, 2005; -5-Confidential manuscript submitted to JGR-Planets Efroimsky and Lainey, 2007;Nimmo and Faul, 2013;Khan et al, 2018], Io [Hussmann and Spohn, 2004;Bierson and Nimmo, 2016;Renaud and Henning, 2018], Iapetus [Peale, 1977;Robuchon et al, 2010;Castillo-Rogez et al, 2011], Europa [Moore and Schubert, 2000;Hussmann and Spohn, 2004;Wahr et al, 2009;, Ganymede Kamata et al, 2016], Enceladus [Roberts and Nimmo, 2008;Choblet et al, 2017], and exoplanets [Henning et al, 2009;Efroimsky, 2012b;Renaud and Henning, 2018], studies that quantitatively investigate several viscoelastic models concomitantly by formulating the problem in a geophysical inverse sense have yet to be undertaken.…”

Ocean tidal heating in icy satellites with solid shells

“…9 and 10 summarize the surface displacement results for Europa and Enceladus. The phase lag due to the delayed ocean response can be significantly larger than the phase lag due to the viscoelastic behavior of the shell (e.g Moore and Schubert, 2000;Kamata et al, 2016)…”