Abstract DGP2026-30

Investigations of ice-shell deformations have been commonly used to provide information on the interior structure and evolution of icy moons (e.g., Nimmo et al., 2002, Peterson et al., 2015). The most commonly used approach is to fit a flexural signature, observed in a stereo-derived topographic profile, to an elastic plate model in order to infer the local elastic thickness of the ice shell. The elastic thickness parameter is directly related to the rigidity and thermal state of the ice shell, and can thus be converted to a heat flux (e.g., McNutt, 1984). Knowing the heat flux at the time the deformation occurred is critical to determine the geodynamic history, longevity of a putative interior ocean, and habitability of the icy body (Vance et al., 2023).

The widespread use of this approach lies in its quick analytical expression, allowing to test various parameters at multiple locations (e.g., Turcotte & Schubert, 2002). However, it remains unclear whether purely elastic plate models can be used to reliably predict the flexure of an elastic-plastic ice shell. Simplistic approaches have further been used to relate the elastic thickness to the heat flux, including the use of a Deborah number to approximate the interior temperature (Nimmo et al., 2002).

In this work, we calculate elastic-plastic flexural profiles that solely depend upon the ice shell’s heat flux and compare them to elastic models. We show that purely elastic models predict unrealistic oscillations near and in the flexural bulge region, with implications for the inferred elastic thickness and heat flux. We further reveal that using the Deborah number approach leads to a substantial overestimation of the heat flux, with examples at Ganymede (Nimmo et al., 2002) and Ariel (Peterson et al., 2015), which has implications for the geologic history of these worlds.

 

McNutt, M. K. (1984). Lithospheric flexure and thermal anomalies. J. Geophys. Res.: Solid Earth, 89. doi: 10.1029/jb089ib13p11180.

Nimmo, F.,  Pappalardo, R.T., & Giese, B. (2002). Effective elastic thickness and heat flux estimates on Ganymede, Geophys. Res. Lett., 29(7), doi:10.1029/2001GL013976.

Peterson, G., F. Nimmo, and P. M. Schenk (2015). Elastic thickness and heat flux estimates for the Uranian satellite Ariel, Icarus 250, doi: 10.1016/j.icarus.2014.11.007.

Turcotte, D. L. and G. Schubert (2002). Geodynamics. Cambridge University Press. doi: 10.1017/cbo9780511807442.

Vance, S.D. et al. (2023). Investigating Europa's Habitability with the Europa Clipper, Space Sci. Rev. 219(8). doi: 10.1007/s11214-023-01025-2.