On the slopes of Mount Sharp, NASA's Curiosity rover has photographed a Martian surface etched into honeycomb-like polygonal fractures — geometric scars left, scientists believe, by ancient mud that once dried and cracked beneath a wetter sky. The discovery adds another layer to a growing portrait of Mars as a world that once harbored liquid water, organic chemistry, and perhaps the conditions necessary for life. Billions of years separate us from that Mars, but the stones remember, and we are only now learning to read them.