Color may have a bit to do with it but I think the real reason is that there are objects in the Rio picture which we can easily recognize. We know
they are cars and buses because of the context but there isn't really thing about them that tells us that. If you can find a similar resolution image
of a desert I'm not sure it would appear so "sharp".
I wouldn't expect miracles from the cameras they are using on GRAIL. They are quite small and the
lenses aren't very big. I know there are some pretty amazing devices out there, but these just don't look like they will show us anything new.
Thank you for your back-and-forth on the resolution issue. I've seen it argued elsewhere, but until now I haven't seen anyone try to get to the
bottom of why images of the similar resolution create such wildly different impressions. Good job, both of you!
The best images I have seen so far taken by a black ops satellite are the call-signs of a few Russian planes and that was in the early nineties. We
are now 20 years further in time, so maybe meanwhile they now can read a newspaper headline from space. I would not immediately say that they
cannot.