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Change Detection on Enceladus

Presentation #303.05 in the session Enceladus (Oral Presentation)

Published onOct 23, 2023
Change Detection on Enceladus

Saturn’s small moon Enceladus has drawn interest since the return of Voyager images showed its complex surface features and limited cratered areas. With the arrival of the Cassini mission, there was confirmation of a plume of material jetting off Enceladus (e.g., Hansen et al., 2006; Porco et al., 2006), the likely presence of a subsurface liquid water ocean (e.g., Čadek et al., 2016), and measured amounts of the elements needed for life (e.g., Waite et al., 2009; Postberg et al., 2023). These characteristics have kept the moon as a focus of scientific study. The comparatively young, smoother and fractured areas of the surface, along with the active plume, suggest recent surface processes are at work on Enceladus. This study focuses on investigating Cassini and Voyager images of this moon to find evidence for and constrain the rates of surface geological changes.

The Voyager 2 mission, which imaged Enceladus in 1981, and the Cassini mission, which made observations multiple times between 2005 and 2017, provide two separate time scales to look for possible changes on the surface. We can consider the ~25 year difference between the two missions, and then the up to 12-year difference between images taken over the course of the Cassini Mission.

While there has been no strategic effort to examine Enceladus for surface change, Phillips et al., (2000), compared Voyager and Galileo images for evidence of plumes and surface processes on Europa. Drawing on the methods of that previous work, we perform a strategic survey of Cassini images to search for changes. This process involves identifying, aligning, and then comparing pairs of images of the same regions on the surface from separate time periods. We also account for differences in resolution and lighting, which is essential for change detection on icy moons (e.g., Neish et al., 2012; Phillips et al., 2000). Directly observed changes, such as differences in brightness or morphology, will provide evidence of active surface geological activity.

Even in the absence of observable changes, this study will help constrain the possible rates of surface processes. At the conclusion of the project, we will be able to provide rate limits on surface processes for multiple examined terrains, helping us understand both potential geologic activity and the detectability of such activity.

Čadek, O et al., 2016. GRL. 43(11)

Hansen, CJ et al., 2006. Science, 311(5766)

Neish, CD et al., 2012. Icarus, 221(1)

Phillips, CB et al., 2000. JGR: Planets, 105(E9)

Porco, CC et al., 2006. Science, 311(5766)

Postberg, F et al., 2023. Nature, 618(7965)

Waite Jr, JH et al., 2009. Nature, 460(7254)

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