Why does the moon 'peel' away from the horizon in this photograph?
Looks like an inferior mirage to me.

This:

https://aty.sdsu.edu/explain/simulations/inf-mir/Kaplan_photos.html

Has a work through for the disk of the sun but I think the same general principles apply here as well.

The specific effect will be somewhat different since in the image from space rays are moving from space down into and through the atmosphere, and then back up again, whereas in the image below the rays terminate at the Earth's surface.



Simulation and photograph from Andrew T. Young's page Photographs of an Inferior-Mirage Sunset: 


  The inferior mirage is very clearly shown in a series of sunset images taken by George Kaplan, of the U. S. Naval Observatory. Here, I describe what's seen in these images, which are actually on the Naval Observatory's website. They are such a “textbook example” of the inferior-mirage sunset that I begged for some details, and permission to show the images here.