Peppered around lava flats and mountaintops all over the moon are strange sinuous shapes known as lunar swirls. Their winding, dusty curves are brighter than the surrounding area and, so far, their formation remains a mystery to scientists.

“They look like someone took a white paintbrush and painted across the moon,” says Catherine Neish, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. She helped organize the 2011 Lunar Swirls Workshop Without Walls, an online conference dedicated to these puzzling features. At the meeting Sept. 7,...