Just when you think you've got the hang of things, the solar system or universe will show you something you've never seen before.
Case in point: What are those little black things on Mars -- where do they come from each spring, and where do they go when winter approaches?
Now, I know I've been running a fever -- it's early-voting-and-flu season here -- and been having trouble with gravity thanks to inner-ear plumbing, but black, spidery things on Mars?
Apparently so, and they've been showing up for their meager sunbathing rites for about a decade that we know about, at least.