All the images in this set showed the interesting terminator irregularity in the S hemisphere. It is clearest in the first image, R from 02:38, and I have given an enlargement of that one. Comparing with other published images from the same night, I believe this is due to straight N-S ranges of cloud over the Tharsis Montes casting shadows. The irregularity seen here is a combination of a bright line of cloud catching the light, and its shadow preceding, with another high bank of cloud to S just going over the terminator.