Apollo 15.
Apollo 15 (July 26 – August 7, 1971) was the fourth crewed mission to land on the Moon. It was the first J mission, with a longer stay on the Moon (July 30 – August 2) and a greater focus on science, including the first Lunar Roving Vehicle. David Scott and James Irwin landed near Hadley Rille and spent 18+1⁄2 hours on extravehicular activity, collecting 170 pounds (77 kg) of surface material. At the same time, Alfred Worden orbited the Moon, operating the sensors in the SIM bay of the service module. During the return trip, Worden performed the first spacewalk in deep space. The Apollo 15 mission splashed down safely, with all goals accomplished, but was marred when it emerged that the crew had carried unauthorized postal covers to the lunar surface, some of which were sold by a West German stamp dealer. The crew was reprimanded for poor judgment, and did not fly in space again. The mission also saw the collection of the Genesis Rock, thought to be part of the Moon's early crust, and Scott used a hammer and a feather to demonstrate Galileo's theory that absent air resistance, objects fall at the same rate regardless of mass.
