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Crustal deformation derived from repeat-pass Interferometric SAR at Enceladus – why and how?

Presentation #210.07 in the session Ocean Worlds: Tectonics, Surfaces, and Ionospheres (Oral Presentation)

Published onOct 23, 2023
Crustal deformation derived from repeat-pass Interferometric SAR at Enceladus – why and how?

The current Decadal Survey aspires to understand dynamic habitability of Ocean Worlds, including their physical and mechanical nature. For Enceladus, these goals suggest that we should: 1) understand how the ocean is maintained over time, 2) infer ocean density (a key constraint on compositional models), 3) ascertain how nutrients are cycled into the ocean, and 4) understand current modes of tectonic deformation and to what extent present-day tectonic activity represents the past. Intertwined in all these questions is the extent of spatial variations in the thickness of the ice crust and how they are maintained. From systematic time series of surface deformation that sample the response of Enceladus to well-understood tidal forcing, one can: 1) derive highly resolved variations in ice thickness, and thus ocean density and thickness of the conductive ice layer, 2) understand the mechanical nature of the tiger stripes (i.e., geometry as a function of depth, nature of mechanical coupling, etc.), 3) discern the rheological nature of the ice crust, and 4) detect the presence of any secular motions. A novel approach to making such deformation time-series is based on repeat-pass Interferometric SAR (InSAR) – a well-established method in the Earth science community. There are no insurmountable technical requirements for making such measurements at Enceladus. Assuming a short campaign (< 1 yr) and ~40 m/pixel resolution over 100-km-scale images, we predict that InSAR time series can measure tidal deformation at accuracies of a few mm—sufficient to resolve tidal displacements (on the order of 10s of centimeters) and to distinguish between models for the plumbing of the tiger stripes (e.g., whether they penetrate the entire ice shell or are associated with intra-crustal reservoirs). InSAR can measure the tidal phase lag to an accuracy of 0.1°, which constrains the magnitude of tidal heating. In addition, sensitivities to secular motion of ~1 cm/yr (or ~1 mm/yr for 400 m/pixel) are sufficient to test if plate tectonic-like motion occurs and could contribute to cycling of nutrients through the ice shell. Thus, InSAR observations can be a key contributor to any assessment of the dynamic habitability of Enceladus.

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