The day's next task was to deploy the Apollo Lunar Surface Experiments Package (ALSEP); while they were parking the lunar rover, on which the TV camera was mounted, to observe the deployment, the rear steering began functioning without explanation. While deploying a heat-flow experiment (that had burned up with the lunar module "Aquarius" on Apollo 13 and had been attempted with limited success on Apollo 15), a cable was inadvertently snapped after getting caught around Young's foot. After ALSEP deployment, they collected samples in the vicinity. About four hours after the beginning of EVA-1, they mounted the lunar rover and drove to the first geologic stop, Plum crater, a crater on the rim of Flag crater, about across. There, at a distance of from the LM, they sampled material from the vicinity of Flag crater, which scientists believed penetrated through the upper regolith layer to the underlying Cayley Formation. It was there that Duke retrieved, at the request of Mission Control, the largest rock returned by an Apollo mission, a breccia nicknamed Big Muley after mission geology principal investigator William R. Muehlberger. The next stop of the day was Buster crater, a small crater located north of the larger Spook crater, about from the LM. There, Duke took pictures of Stone Mountain and South Ray crater while Young deployed a magnetic field experiment. At that point, scientists began to reconsider their pre-mission hypothesis that Descartes had been the setting of ancient volcanic activity, as the two astronauts had yet to find any volcanic material. Following their stop at Buster, Young did a demonstration drive of the lunar rover while Duke filmed with a 16 mm movie camera. After completing more tasks at the ALSEP, they returned to the LM to close out the moonwalk. They reentered the LM 7hours, 6minutes, and 56 seconds after the start of the EVA. Once inside, they pressurized the LM cabin, went through a half-hour briefing with scientists in Mission Control, and configured the cabin for the sleep period.