The old and the new
When you have a massive impact on an ice moon the repercussions reverberate outward and leave tell tale cracks and compression zones in the the ice like ripples on a pond.
Such is the case with Valhalla crater on Callisto.
The crater in the middle is flattened out due the more fluid like properties of ice compared to rock.
Later more recent impacts now overlay the much older crater like pockmarks.
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