From Death Valley to Chile to Iran, similarly sized polygons of salt form in playas all over the world — and subterranean fluid flows might be the key to solving the long-standing puzzle of why.

NASA's Curiosity rover snapped this view of polygon-patterned bedrock on May 4. Mars is home to a lot of odd-shaped rocks that can look pretty random. Patterns, however, can catch scientists’ eyes.

A study of medieval Islamic art has shown some of its geometric patterns use principles established centuries later by modern mathematicians. Researchers in the US have found 15th Century examples ...