Understanding The Structure Of Enceladus’ Ice Shell

By Keith Cowing
Press Release
February 24, 2023
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Understanding The Structure Of Enceladus’ Ice Shell
Shell thickness model based on Tajeddine et al. (2017) and Čadek et al. (2019); a global view in Mollweide projection (left) and a zoom of the south-polar region in stereographic projection (for colatitudes 140°–180°) (right). AGU JGR

Enceladus is a dynamic icy moon of Saturn and a leading target for future planetary missions focused on the search for life beyond Earth.

For such missions, instruments that can provide geophysical and geochemical context for ice shell and ocean processes are critical to evaluate whether conditions are suitable for life and biosignature detection.

Radar sounding is a powerful geophysical technique to probe the thermophysical and chemical properties of icy moons, like Enceladus, and to investigate the subsurface context for the exchange of material and energy between their subsurface oceans, ice shells, and plumes.

To inform the scientific potential and instrument performance demands of such a radar-sounding investigation of Enceladus’ ice shell, we adapt and extend previous radar attenuation analysis done for Europa to the configuration and conditions of Enceladus.

We also discuss how attenuation (both as an obstacle for the detection of ice shell reflectors and as a signal itself) can help constrain the thermal, physical, and chemical configuration of Enceladus’ ice shell and reveal the processes governing the moon’s ocean/shell/plume system.

Key Points

We explore radar attenuation within Enceladus’ ice shell as a function of its chemistry using a 3D model of its shape and thermal structure

Direct radar detection of the ice-ocean interface is improbable for chloride-rich shells except for the thin south-polar region

The NH3 eutectic isotherm is a comparatively easy-to-detect interface, with the potential to constrain the shell thickness and composition

Full paper: Radar Attenuation in Enceladus’ Ice Shell: Obstacles and Opportunities for Constraining Shell Thickness, Chemistry, and Thermal Structure, JGR Planets (open access)


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