The Lunar Reconnaissance Orbiter has a great blog where they post images from the hi-res camera onboard. I was perusing a recent image, and was a bit befuddled:
What the heck? Is this a plateau of some kind? Is that a small dome just below the center of it? The whole thing looks pitted around the edge, too, like some sort of erosion has taken place. But that can't be right! Happily, being an old hand with optical illusions, I knew exactly what to do. I flipped the image over, and all became clear:
Ah, that's better. Now you can see what's what: it's a crater with boulders in it. The small dome is now clearly a tiny meteorite impact crater. What looked like pitting is now obviously rocks and rubble that have slid down the slope of the crater wall. This is an old illusion. Having evolved on the ...
