From what I can gather thus far it could be a noctilucent cloud enhanced by some kind of edge effect associated with being just past conjunction. It’s the right area as well for that. On the other hand, it seems transient and very high, and even looks like a big impact plume in one of the images. This is an ultimately falsifiable hypothesis given enough time to reimage the area, which is quite large and could take quite a while. I haven’t heard anything else lately, but there is an extensive speculation thread going over at Above Top Secret, which, besides the occasional nuttiness and silliness, seems fairly rational.