Icy Worlds

Gravity-Induced Ice Compaction and Subsurface Porosity on Icy Moons

By Keith Cowing
Status Report
November 20, 2023
Filed under , , , , , , , ,
Gravity-Induced Ice Compaction and Subsurface Porosity on Icy Moons
Evolution of the compaction coefficient λ(η, t) with the ice viscosity and the compaction time. The average ice compaction coefficient measured on Earth is given by the yellow line λ = 5.5 × 10−6 Pa−1 . Black square represents the location of the Antarctica A2 dataset in this graph, estimated from the local accumulation rate of snow. White square represents our scenario for Europa, where the compaction time is taken to be the ice crust age and for a viscosity of η = 1021 Pa s [23]. — astro-ph.EP

Our understanding of the surface porosity of icy moons and its evolution with depth remains limited, including the precise scale at which ice compaction occurs under self-weight pressure.

This parameter is of crucial interest for the correct interpretation of current remote sensing data (spectroscopy in the visible, infrared to passive microwave) but also for planetary exploration when designing a lander, a rover or a cryobot. In situ exploration of the ice crust would require knowledge about subsurface porosity. This study employs a compaction model solely driven by overburden pressure based on prior research. The formulation for density as a function of depth, incorporates an essential parameter: the ice compaction coefficient.

To determine this coefficient, we fit our depth-dependent density model to existing data obtained from Earth-based measurements of ice cores in Antarctica and North Greenland. Our results yield a typical lengthscale for ice compaction on Earth of approximately 20.1 ± 0.6 m , consistent with the existing literature. We apply the model to Europa, which due to its lower gravity, has a typical ice compaction scale of 150 ± 4 m. We compare it with the depths scanned by current spaceborne data and find that porosity can be considered constant when accounting only for gravity-induced compaction.

Cyril Mergny, Frédéric Schmidt

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
Cite as: arXiv:2311.10627 [astro-ph.EP] (or arXiv:2311.10627v1 [astro-ph.EP] for this version)
Submission history
From: Cyril Mergny
[v1] Fri, 17 Nov 2023 16:28:33 UTC (561 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻