OMFSM. I love this picture. Love love love. Love.
[Click to embiggen.] Is it a ring of fire on Mercury? A look into the gateway of hell? A promo for Halo 3? Nope. It's far cooler: it's the rim of the lunar crater Erlanger poking into the sunlight. Erlanger sits almost at the Moon's pole, lying at a latitude of 87° north. At that latitude, the Sun is forever near the horizon, only getting a little above or below the limb depending on the Moon's orbit around the Earth. In this case most of the crater is not lit by the Sun, but the raised rim gets up just high enough to see some sunlight, illuminating it in this wonderful way. Note the small patch of lunar surface to the lower left of the picture that's in sunlight as well. That's another indicator that how much sunlight you get at ...
