The Last Days of MESSENGER

The MESSENGER Mercury probe is in the news again, this time for two somewhat related items. The spacecraft has been orbiting the closest planet to the Sun since March 2011, just over four years ago, and has been returning amazing data ever since. It achieved a numerical milestone recently: its 4000th orbit of the little world. In that time it's sent over a quarter million images of Mercury back to Earth, an astonishing feat. Because Mercury is so close to the Sun it's hard to study from Earth, a...