Exploring the Limits of Isostasy In Icy Worlds: Ice Shell Basal Topographic Flow Across the Solar System
Abstract
The ice-covered ocean worlds of the solar system have a diverse array of ice surface temperatures, shell thicknesses, and surface gravities, but have one thing in common: they all have a layer of warm, low-viscosity ice at the ocean interface that can flow to eliminate topographic relief at the interface. For previously-studied large icy worlds (Europa), this flow can flatten out topography at the ice/water interface in centuries to millennia, making it almost impossible to support ice-surface topography via Airy isostasy. In addition to the profound implications for surface geomorphology, the possibility that there might be no "thin spots" in the ice is important for both astrobiology and future exploration efforts.
In this work, we use the Icy Satellite Basal Topography Model (ISBTM) to more broadly explore the scaling laws for basal flow across a range of shell thicknesses, thermal profiles, horizontal lengthscales, and surface gravities, with the goal of understanding the limits of isostatic adjustment for icy ocean worlds in general. We compare these results with previous analytical work from the Galileo era and other modern ice shell models. By combining thermal buoyancy-driven flow, modern viscosity formulations, and a free bottom surface, ISBTM has the unique ability to model both basal topographic flow and solid-state diapiric convection simultaneously. We describe how these processes interact: diapirism can cause small variations in topographic relief, and topographic flow triggers and focuses diapirism. An important limitation of previous versions of ISBTM has been a fixed upper boundary condition: the brittle upper lid is assumed to be rigid. We present the early results of efforts to incorporate mobile-lid resurfacing into the model.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P53D3481G
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHERE;
- 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6221 Europa;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6282 Enceladus;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS