Cycloidal and Wavy Lineaments on Europa from Diurnal, Obliquity, and Nonsynchronous Rotation Stresses in a Visco-Elastic Ice Shell

R.T. Pappalardo (1) , D.A. Patthoff (1) , J. B. Li (2, 1) , B.J. Ayton (1) , David Dubois (1, 3)

1 JPL - Jet Propulsion Laboratory
2 CS CALTECH - Computer Science Department
3 PLANETO - LATMOS

Introduction: Jupiter's icy moon Europa displays a variety of lineament types ranging from arcuate to " wavy " to cycloidal. While some have suggested that cycloidal fractures form as a result of tail crack propagation in a rotating diurnal stress field [1-3], most previous studies have attributed the cycloidal shapes to the eccentricity (diurnal) tidal stresses that Europa experiences as it orbits Jupiter [4-6]. More recently, obliquity stresses have been explored as a mechanism for creating cyloids [7]. The stress resulting from eccentricity or obliquity tides is relatively small (10s kPa) and could combine with other stressing mechanisms , such as nonsynchronous rotation (NSR) [8-10]. Previous work has invoked simulations of diurnal and added obliquity stress to explain Europa's observed cycloidal lineaments. However, these models assumed an elastic ice shell, and neither of these two stress mechanisms alone can simulate Europa's wavy lineaments. Preliminary elastic-shell modeling [8,9] of diurnal stress and added NSR stress suggested that combining diurnal and NSR stress might be key to explaining " wavy " lineaments, as the NSR reduce the diurnal fluctuation of stress that results in cycloid cusps. Subsequently, it was found that small amounts of NSR stress might have contributed to the formation of cycloids but that significant NSR was not necessary to account for their planform shape [10]. Here we expand on previous elastic-shell modeling [8, 9] to demonstrate that NSR can combine with diur-nal and obliquity stresses to create cycloidal linea-ments or lineaments with a " wavy " planform, as simulated with the viscoelastic model SatStress [11]. These stress mechansims could combine to produce the observed range in planform morphology of Europa's line-aments, from cycloidal to wavy to arcuate. Model: We employ an updated version of SatStressGUI [12] that assumes a four-layer visco elastic satellite. We assume an ice density of 920 kg/m 3

Domaines: Planétologie; Géophysique [physics.geo-ph]

R.T. Pappalardo, D.A. Patthoff, J. B. Li, B.J. Ayton, David Dubois. Cycloidal and Wavy Lineaments on Europa from Diurnal, Obliquity, and Nonsynchronous Rotation Stresses in a Visco-Elastic Ice Shell. LPSC 2016 - 47th lunar and planetary science conference, Mar 2016, Houston, United States. pp.2712. ⟨hal-01274499⟩