" Here are two versions of an image that is a stack of four images obtained 15 seconds apart on June 6 at a range of 45.8 million km. Here they have been enlarged by a factor of four. ...
"The right version has been sharpened using RegiStax. The sharpened version reveals a diagonal dark band on Pluto - it's now absolutely certain that this is a real feature. In contrast, the apparently brighter terrain at the right limb is almost certainly a processing artifact. Charon may be starting to show large scale markings, i.e. possibly very slightly darker terrain in its upper left 'quadrant'. But this could easily be an image processing artifact.
...
"It wouldn't surprise me if small dark spots started appearing within the bright terrain at much higher resolution and/or small bright spots started appearing within the dark terrain."
Bjorn Jonsson http://www.unmannedspaceflight.com/index.php?s=f65bb4f467e2cf3d2d7919bd2b76c127&showtopic=7970&st=240&p=221117&#entry221117