Mapping and Classification of Enceladus’s Linear Structures

Enceladus, Saturn’s sixth-largest moon (diameter: ~504 km) [1], is one of the geologically active bodies of the Solar System. Its icy shell its characterized by linear structures of tectonic origin that are the focus of this study [2]. With this work our intent is to provide an example of methodical mapping and classification of the geomorphological features characterizing the outer shell of an icy satellite.

We mapped the single structures and families of structures – characterized by the same direction and possibly originated in the same tectonic event – at four locations – referred to as ‘areas of interest’ – sit in two out of the four geological provinces identified in [3]. Each area of interest had all the sides measuring 20° and contained one structure already identified. This choice was made to ensure the correct understanding of all the others structures since the study was conducted only using the available Cassini global mosaic (resolution 110 m/px) [4]. The classification method used in this work was the one proposed in [5] with Enceladus’s linear structures falling under five classes: scarp, trough, band, ridge, and chasma.

We managed to identify a total of 69 between single structures and families of structures. They were classified into the aforementioned morphological categories based on their geometric characteristics after an analysis of their cast shadows. Due to the limited resolution of the available data and the absence of an available DTM at the time of the study, 7 of them remained undefined. Among the other 62, the vast majority (56) was identified as falling under the ‘trough’ class (11 of them were additionally sub-classified as ‘pit chains’), whilst 3 of them where chasmata, 1 was a band, and 1 was a scarp. We also managed to sketch a relative timeline for each area of interest by using the cross-cutting relationships existing between the structures. Main and secondary periods were defined to give a better understanding of the tectonic evolution of each area of interest.

Our study, although moderate in its extent, represents a solid attempt at applying a methodical mapping process for an icy satellite. We provided a classification for a number of structures whose class had not yet been defined and theorized a possible tectonic evolution for each area based off the geomorphological cues at our disposal, setting up a possible workflow for future studies on other similar bodies in the outer Solar System.

REFERENCES:

[1] Thomas, P. C. (2010). Icarus, 208, 395–401.

[2] Spencer, J. R. and Nimmo, F. (2013). The Annual Review of Earth and Planetary Science, 41, 693–717.

[3] Schenk, P. M., Clark, R. N., Howett, C. J. A. Verbiscer, A. J., Hunter Waite, J. (2018). University of Arizona Press, ‎536 pages.

[4] Bland, M. T., Becker, T. L., Edmundson, K. L., Roatsch, T., Archinal, B. A., Takir, D., et al. (2018). Earth and Space Science, 5, 604–621.

[5] Nahm, A. L. and Kattenhorn, S. A. (2015). Icarus, 258, 67–81.