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Polygonal Impact Craters on Ganymede

Presentation #315.02 in the session Icy Satellites: Surfaces, Ice Shell, and Interior (Poster)

Published onOct 23, 2023
Polygonal Impact Craters on Ganymede

Introduction

Polygonal impact craters (PICs) are unique geological features observed on various planetary bodies, and constitute a small percentage of the impact crater population [1]. This study focuses on PICs on Ganymede, where no such craters have been investigated so far. PICs have at least one straight rim segment in planform [2]. In this study we present the distribution of PICs, examine their morphological characteristics and investigate the causes for their polygonal shapes.

Data

We used the new global mosaic, which combines the best high-resolution images from Voyager 1, Voyager 2, Galileo, and Juno spacecrafts [3].

Results

About 459 PICs were identified and mapped. Among them 215 were found on dark terrain, 210 on light terrain, 33 between dark and light terrain, and 1 PIC on reticulate terrain. About 157 PICs have a central peak, 124 have a pit, and 5 contain a central dome. For the rest of the PICs central features are missing, partly due to insufficient resolution. In case of PICs from light terrain, we found 58% of straight rim segments aligned parallel with their adjacent linear features. In case of PICs from dark terrain, we found that 55% of straight rim segments aligned parallel with their adjacent linear features.

Conclusions

This study is the first report and analysis of PICs on Ganymede. All of the mapped PICs are complex craters. The PICs attain their final shape during the modification stage of cratering where preexisting fractures and faults planes govern via slumping/downfaulting. The comparative analysis of the orientation of PICs straight rim segments and adjacent linear features indicates that there exists genetic relationship between PICs and linear features. This implies that linear features are not only surface markers but act as mechanical anisotropies and zones of crustal weaknesses.

References:

[1] Öhman, T., et al.: Polygonal impact craters in the solar system: Observations and implications, 2010. [2] Beddingfield, C. B., et al.: Icarus, 274, 163-194, 2016. [3] Kersten, E., et al.: EPSC2022-450, 2022.

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