[MayeulC]

there seems to be excessive distorsion at the poles. Is this for a lack of data, or is it due to the coordinate system?

The poles are the most interesting part to me, but there doesn't seem to be a way to control lighting, so they are at least partially obscured. Moreover, I'd have expected the terminator to be less fuzzy due to Mars' thin atmosphere, but it might be just me.

[OmicronCeti]

The coordinate system changes from equirectangular to polar stereo. The poles just don't get good imagery from the MRO. I work extensively with HiRISE data which is collected from the same orbiter as the CTX data this map uses.