Take this image for example. Is this a seal hide, or a satellite image of dune gullies?
It's the latter, obviously, as photographed by NASA's HiRISE camera – but if I hadn't primed you, you may never have guessed "planet surface" at all, right? Like, if someone showed you this photo and told you it was a close-up view of a gorilla's hand, would you really recant with "Well no, actually, that's an aerial view of Mars' Moachis Terra region"? Of course not. You'd probably say "Those are balls. This close, they always look like landscape. But nope, you're looking at balls."
Via the HiRISE project's always stunning (if sometimes ballish-looking) Beautiful Mars Tumblr.