Yesterday was the Mars Reconnaissance Orbiter HiRISE team's latest flood of archived images, 1,025 of them. You can browse them all here; they are provided with titles but most have little other descriptive information. I figured most people would browse the pages sequentially and not get through all 65 pages of thumbnails. Knowing I wouldn't scan them all either, I skipped forward to page 42 (what other number would I pick?) and started browsing from there. I saw gorgeous sand dunes, some pretty incredible recent gullies eroding crater walls and depositing fans onto crater floors, and lots of other cool stuff; but the image below won the prize for weirdness.
It's an impact crater, of course; the shape of the walls of the crater isn't anything unusual. But what the heck is going on in the crater floor? Here's a closeup:
This isn't like the center of any other crater I've ever seen, with its wrinkly fractures and flow features. At least they look flow-ish. Flows of what? Lava? Dust? I haven't the foggiest idea. But the pictures are cool, aren't they? Go explore the archive for yourselves to find more cool stuff.