When NASA added a drone called Ingenuity to its Mars 2020 rover Perseverance, it was expected that the tiny 4-pound helicopter would fly a total of five very short missions in the thin Martian atmosphere. But Ingenuity far exceeded all expectations, making dozens of flights before its rotors suffered damage in January. Correspondent David Pogue reports on how a small drone built from off-the-shelf parts continues to provide valuable data and images from Mars three years into its mission.