The second of the Apollo J series missions included a total of 20 hours 14 minutes of EVA on the lunar surface in which Duke and Young deployed the ALSEP and conducted extensive surface travel aboard the LRV. During the surface exploration new lunar terrain data was obtained, along with 209 Pounds of lunar samples. Because of guidance problems and yaw oscillations encountered in the SM propulsion system prior to the landing, NASA decided beforehand to cut the mission short. Having released a P&F satellite in lunar orbit, the CSM returned to earth a day early, splashing down after 265 hours 51 minutes.