Hidden fluid dynamics of dry salt lakes

Dry salt lakes are an extraordinary part of desert landscapes. Their surfaces are often covered by strikingly regular polygonal shapes bounded by narrow ridges. Familiar to millions of tourists who have visited Death Valley, shown in figure 1, or Bolivia’s Salar de Uyuni—Earth’s largest known natural source of lithium—these otherworldly patterns inspired the Star Wars planet Crait, site of the climactic battle of The Last Jedi. Surprisingly, the mechanism by which the polygons form has remained elusive until this past year.