Mario Runco Jr. is an American Earth and planetary scientist and former NASA astronaut who flew three Space Shuttle missions—STS-44 (1991), STS-54 (1993), and STS-77 (1996)—logging over 551 hours in space, including a 4.5-hour spacewalk. Born in the Bronx in 1952, he earned degrees in Earth and planetary science and atmospheric physics before working as a hydrologist, serving as a New Jersey State Trooper, and commissioning as a U.S. Navy officer, where he held roles in meteorology, hydrography, and oceanography. Selected as a NASA astronaut candidate in 1987, Runco supported spacecraft operations, crew escape systems, mission control communications, and ISS-related research facilities, and later served as project manager for the Lunar Habitation Systems Project. During his flights, he conducted military, life sciences, astronomy, microgravity, and technology demonstration experiments, operated the Shuttle’s robotic arm, and contributed to educational outreach. He received multiple military and NASA honors and retired from NASA in 2017. Caption courtesy of NASA.