The Messenger probe, launched in August of 2004, will take more than six and a half years to get to the orbit of Mercury. Even though Mercury is relatively close-by, in order to get there with a minimum of fuel use (allowing the probe to allocate less weight to fuel and more to equipment), Messenger needs to do "gravity assist" flybys of Earth, Venus, and even Mercury itself to gain and shed enough speed to get it into the right orbit. Close flybys aren't wasted -- Messenger trains its high-resolution cameras and sensors on the planets as it passes by.

Earlier this month, Messenger performed its lone Earth flyby, and snapped numerous pictures during its brief encounter. The Messenger website, at the Johns Hopkins University Applied Physics Lab, has the resulting gorgeous high-resolution images of our home; moreover, they have assembled the series into an animation of 24 hours of Earth's rotation, observed by Messenger as it speeds away. Messenger will never be this close to Earth again, and this is a lovely way to say goodbye.

(Thanks, JWZ)