Thanks for the comments and likes, everyone.
Frank, that sounds like my seeing for the past month.
Thanks, Pete--I actually missed some detail on Cimmerium (and Hesperia), but I plead teeny tiny image. At first I didn't know what to make of that dusky area either. I had not previewed Mars before my observation and have sort of been out of touch with what side Mars was presenting (except for your sketches posted here), so I had to study what I was seeing for a while. Once I realized that the dark albedo feature was probably Cimmerium, I figured that the dusky area were those vague features around Elysium (Hyblaeus Extension, Cerberus, Trivium Charontis), and was really there. Elysium is often bright, but not this time. Here is an image by Frank Mellilo made at 0110 UT (9:10 PM EDT on the 30th) that shows those vague features.
http://alpo-j.sakura...3/m230331f1.jpg