Although similar in appearance, Australian fairy circles turn out to behave differently, Dr. Getzin and his colleagues have found. The soil where they form is loamy, not sandy as in Africa, they say. And rather than form a water trough, Aussie circles feature a very hard surface of dry, nearly impenetrable clay, which can reach up to a scalding 167 degrees during the day. Despite the differences, though, they believe the fairy circles’ function remains the same. When the researchers poured water into the circles in a simple irrigation experiment, it flowed to the edges, reaching the bushy grass that grew there.