I see what you are talking about, btbw. But I am still sticking with my two rock theory for two reasons.
1. When you look right before the "bend in the neck", there looks to be a a srtaight edge, going back and to the left (...back and to the left,
back and to the left, back and to the left ...).
That is where the rock in the foreground ends.
2. There is another dark spot in the photo that appears to be a shadow that has no origin. 45degrees off the circled area there is a long straight
dark spot that looks like a shadow. The same discoloration could be used to explain the shadow under "the head".
I would, of course love to be proven wrong and shown that there is, or was, life on Mars. Especially advanced life.