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- Title
Europa's Double Ridges Produced by Ice Wedging.
- Authors
Cashion, M. D.; Johnson, B. C.; Gibson, H.; Turtle, E. P.; Sori, M. M.; Melosh, H. J.
- Abstract
Double ridges are sprawling features observed globally across the icy surface of Europa. They consist of two topographic highs flanking a trough. The topographic relief of the ridges is approximately 100 m, and the ridges extend up to hundreds of kilometers in length. The interior structure and dynamics of Europa's ice shell are currently poorly constrained. Therefore, accurate models for the formation of these prominent surface features can be useful for determining how the ice shell operates. We hypothesize that double ridges form as a result of incremental ice wedging. We use both analytical and numerical finite element models to quantify the deformation that occurs as an ice wedge grows incrementally within the ice shell. We show that incremental growth of the ice wedge results in surface deformation that matches the size and shape of typical Europan double ridges, including their topographic relief and surrounding troughs. We find that as the depth of the ice wedge increases, double ridges become broader and shorter. We explore the possibility of local and non‐local sources for the liquid water that freezes to produce the wedge and ultimately argue in favor of local sources of liquid water within the ice shell. Plain Language Summary: Europa, the second Galilean satellite, is hypothesized to have a global salt‐water ocean underneath its outer icy shell. Double ridges are a common feature on Europa's icy surface. They consist of a long trough bordered on either side by uplifted hills of ice. The height of the ridges above the surface is approximately 100 m, and the ridges may extend for hundreds of kilometers over the surface of the moon. Models that show how surface features, like double ridges, may form can tell us about characteristics of the ice shell and underlying ocean that are otherwise hard to measure. We use two different techniques to model a process for how double ridges might form. In this process, water, possibly from the subsurface ocean, enters a long vertical crack in the ice shell and freezes along the sides of the crack. Over time as water continues to enter and freeze in the same place, a new wedge of ice grows inside the ice shell and pushes on material around it. The ice wedge forces ice at the surface of the shell to deform into the same size and shape of double ridges that have been observed on Europa. Key Points: Numerical modeling suggests that double ridges are produced by wedges of ice that grow within Europa's ice shellAnalytical and numerical models show that an ice wedge within Europa's ice shell elastically deforms the surface into double ridgesIce wedge material may be sourced from the ocean or locally from cryovolcanic dikes or water reservoirs within the shell
- Subjects
VOLCANIC soils; LUNAR surface; FINITE element method; DEFORMATION of surfaces; WEDGES; ICE
- Publication
Journal of Geophysical Research. Planets, 2024, Vol 129, Issue 2, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2023JE008007