Aratus CA is an unusual depression and possible volcanic vent, previously featured in the Apollo Image of the Week. This depression is about 9.5 km long and 3 km wide, located at the termination of a north-south trending wrinkle ridge known as Dorsum Owen. After the mare lavas erupted and cooled, contractional tectonic forces generated wrinkle ridge features. Most lunar scientists think this unique depression is a product of both volcanism and tectonic collapse. Each lobe is distinct, for example, Vallis Lorca is a collapse pit crater, while the lobe to the east named Rima Sung-Mei is a small rille. Stratigraphy and cross-cutting relationships indicate multiple tectonic and volcanic events. The featured image of the Vallis Lorca lobe shows “rings” around the rim, indicative of collapse. Browse the whole NAC image!
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