Comparison of the neck area of comet 67P C-G on images from ESA's Rosetta blog
Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
here with some contrast processing (HDR) applied
|Inset upper left Nov 30, during emission, background Dec 09|
Also the dark "smear" to the left of them seems to be more prominent now.
Comparison of images taken 2014 Nov 30, Oct 02, and Dec 09
|Comparison Nov 30, Oct 02, and Dec 09, 2014|
The interpretation by ESA of the Dec 09 Rosetta NAVCAM image is rather cautious.
Follow the discussion started on the UMSF forum
"The latest Navcam blog shows new - or apparently new - features in the neck. Here's a comparison between October and December images (December on the right). I would suggest a close examination of images would probably show more things like this.
Take a look at the comparative series by Bill Harris