Which Apollo 15 astronaut dropped a hammer and feather on the Moon?

Apollo 15 astronaut David Scott dropped a hammer and a feather on the Moon.

Scott performed the demonstration during Apollo 15’s third and final lunar surface excursion on August 2, 1971. He released a 1.32-kilogram aluminum geological hammer and a 0.03-kilogram falcon feather from roughly the same height, and both struck the ground together.

The Moon’s atmosphere is effectively a vacuum, so there is almost no air resistance to slow the feather. Both objects therefore fell with the same gravitational acceleration, illustrating the equivalence principle associated with Galileo’s studies of falling bodies.

The other Apollo 15 moonwalker, James Irwin, was Scott’s crewmate but did not perform the demonstration. Alan Bean flew on Apollo 12, and Alfred Worden remained in lunar orbit aboard the command module during Apollo 15.