If a prize was ever awarded for the ‘easiest feature to find on the Moon’, it would surely be given to Mare Crisium, the Sea of Crises. It’s so big, so obvious and so well-placed that it actually takes a lot of effort to miss it. Even if you know absolutely nothing about the Moon and its surface features, you’ll have seen Mare Crisium many times already.
It was named in 1651 by astronomer and lunar cartographer Giovanni Riccioli after being known previously as ‘the Caspian Sea’, among other things. Mare Crisium doesn’t just have a special place in lunar science; it’s featured heavily in science fiction, too. It was the setting for sci-fi master Robert Heinlein’s classic story The Moon isa Harsh Mistress. It was also the setting of Arthur C. Clarke’s story The Sentinel, which inspired the film 2001:A Space Odyssey.