What do you do when your spouse is out of town, your children are asleep, and you're annoyed at the world because you've been sick with a cold and sinus infection for two weeks straight with no recovery in sight? Here's what I do: have a few drinks, eat some chocolate, and play with archival space image data. Here's the result of this evening's self-indulgence. Those of you who follow me on Twitter saw the intermediate steps in the process of producing this photo (steps 1, 2, and 3).
NASA / JPL / Emily Lakdawalla
Crescent Neptune and Triton
Neptune was the last planet Voyager 2 passed. As it departed the system in September 1989, it watched the crescent planet (along with its largest moon) diminish. This photo was taken on September 3, about 9 days after the flyby.
Voyager 2 is the only thing we have ever built that has ever seen this huge planet (and its huge moon Triton, not quite but almost as big as our Moon and Europa and larger than Pluto or Eris) from this perspective. There is no government (or private company, for that matter) with any plans ever to do this again. The photos we have from Voyager are very likely the only ones of Neptune from Neptune that I will see in my lifetime. I hope not. I hope we'll go back and get better pictures. Until that happens, we'll have to do the best we can with what Voyager 2 sent us. The good news is, there's a lot more in the Voyager 2 data archive than most people have ever seen. There are 10,000 photos, and while not all of them are great, it's not hard to look at them all to find the great ones.