Statistical analysis of manually segmented linear surface features in Galileo images of Europa

The solid-state imaging experiment onboard the Galileo mission returned around 700 images of Jupiter’s icy moon Europa [1]. These images revealed a young surface that seems to have undergone resurfacing processes, mainly caused by ridges that overprint older ridged terrains [2]. Tidal stress fields from resonances with other Galilean moons and non-synchronous rotation seem to drive geophysical surface processes. Although the Galileo images have undergone substantial study, formation mechanisms of linear surface features and connected to that, the thickness of the ice layer, are not well constrained, but many hypotheses are proposed [3]. However, a statistical analysis of linear surface features in terms of photometric properties has not yet been done.
With this work, we aim to provide a deeper understanding of geophysical processes on the surface of Europa. Furthermore, it is valuable for future mission design and planning, e.g. for the upcoming Europa Clipper mission [4], to find places that show anomalies or that would benefit from further investigations.
We analyse manually segmented linear surface features in selected Galileo images of intermediate resolution (150 - 600 m/px). The surface feature categories we investigate are 1) bands, 2) double ridges, 3) ridge complexes and 4) undifferentiated lineae. Additionally, we also segment cusps, which indicate cycloidal features. Since the cross-cutting relationships are preserved during segmentation, we can gain insights into the geological history. With these segmentations, we can retrieve the length, width and the main direction of each linear feature, while taking the number of overprints into account, in order to analyse the tidal stress field and its development over time. We look into differences in radiance between the different linear surface features with respect to the geological history to learn about endogenic and exogenic processes. More specifically, we extract radiance profiles along the direction of maximal change. For double ridges for example, we extract a w-shaped profile that let’s us investigate symmetry and differences between instances of double ridges. These analyses could turn out useful in constraining formation mechanisms for linear surface features and in reconstructing the geological history of Europa’s surface. The current status of our work is presented.
References:
[1] Belton, M. J. S., et al., The Galileo solid-state imaging experiment, Space Sci. Rev., 60, No. 1/4, 413-455.
[2] Greeley, R., et al., Europa: Initial Galileo Geological Observations, Icarus, Vol. 135, No. 1, 4-24, 1998
[3] Daubar, I., et al., Planned Geological Investigations of the Europa Clipper Mission, in prep.
[4] Richey, C., et al., The Europa Clipper Mission: Science Objectives and Mission Status Update, AGU Fall Meeting Abstracts, 2018