Some hawk-eyed folks recently spotted a decidedly rat-like critter in a photo taken in September last year by the Curiosity Rover. It’s really a rock. I guess it would make a pretty good pet rock. Some fans have set up a Twitter account for it with the appropriately dire warning ‘People of Earth. You found me. Prepare for invasion’ as its profile. OK, guess I know what’s going into the basket next time I’m at the supermarket: rock cheese.