Looping Network Meetings

#68 April 28, 2025

Monday 15:00 (Paris/Warsaw time)

Sophie Silver (University of Pennsylvania)

Decoding planetary surfaces by counting cracks

Abstract:
Thin fractured films are ubiquitous across our solar system. We have recently used a geometric characterization of fracture networks that counts cracks and their intersections. We discovered that natural fracture mosaics, both on Earth & on other planets, form three clusters that each lie close to three respective end-member geometries: (i) hierarchical crack networks with geometry similar to laid brick (rectangular cells, T junctions); (ii) ”Voronoi” networks with hexagonal cells and Y junctions; and (iii) ”grid paper” networks in which cracks overprint other cracks (rectangular cells, X junctions). We hypothesized that networks (ii) and (iii) evolve under conditions in which water plays a role in ”refreshing” crack dynamics: cyclic volume change drives node twisting (T − > Y), relevant for mudcracks and polygonal ground; and crack healing by refreezing allows overprinting, a dominant process for fractured ice sheets. As such, the existence of these patterns on other planetary surfaces betrays the presence of water. We test these hypothesized dynamics using laboratory experiments on analog systems of mudcracks and ice sheets.

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