Here’s a very recent (7-12-2015) picture of
Pluto Charon that shows a bright circular feature near 1 o’clock with a long white streak heading down and to the right for a very long way – possibly even as much as half the diameter of the entire planet. If you look near the top of the image, you can see that it’s partly in shadow, and the low angle of the light from the Sun exaggerates vertical elevation changes much as they do here on earth just after dawn and before sunset. So we can see that the upper portion of the surface of Charon Pluto appears to be very irregular and not precisely spherical.
Which should be no huge surprise, given how small Charon
Pluto really is (only 1200 2300 km across, or about 750 1400 miles, which is much smaller than our own Moon (Luna or Selene), in fact less than the distance from my town (Washington DC) to Miami. In this image the ‘top’ of the planet looks almost like a somewhat-rounded 7-sided heptagon rather than a sphere.
It appears to me that the object (asteroid or comet or whatever) which smacked Charon
Pluto and formed that large crater came not along a radius, but at some other angle — I’d have to do some experiments to see whether the object came, so to speak, from somewhere off to our right and from our back as we view the image, or from the exact opposite direction, from above and in front of us, perhaps a bit to our left. I just don’t know if the debris from such an impact would fly back in the direction from which the impactor came, or whether it would continue going forward in the direction of the impactor. It’s fun to do experiments with sandboxes and lofting various projectiles, but you never know how well your set up will match reality. Sand and water at room temperature probably don’t act the same way as the surface of Pluto (various types of frozen ices, at its insanely cold temperatures), being hit by something that vaporizes and melts solid rocks by the tremendous force of impact!
I got the image from here. And thought this was a picture of Pluto. But it’s not.