I've got a new candidate for "Coolest Picture Ever" today: an image shot by the Messenger space probe from 114 million miles away showing, at lower left, our Earth and Moon.
As NASA explains here, Messenger wasn't really aiming for us. We just happened to fall into its field of view as it searched for small asteroids in the neighborhood of Mercury, which it was sent to explore.
What I love about this picture is that it shows how we essentially live on a rare double planet. Our moon is unusually large in proportion to its mother planet (there are bigger moons in our solar system, but they accompany much bigger worlds). Being able to look up and see our satellite as a sphere with surface craters and mare, rather than a featureless bright light moving through the sky, is a rare gift we take for granted because we grew up here. And that's not even counting the fact that it has just the right orbit and size to perfectly eclipse the Sun, a one-in-a-jillion coincidence itself! If there were such a thing as alien tourists, they might travel halfway across the galaxy to see such a wonder. And its impossible to guess how different life on Earth would be--or if there'd even be life at all--without it.
The very best Best Pictures Ever remind us to look around once in a while and marvel.