Many people consider Apollo 15 to be the crowning glory of the Apollo programme in terms of science. It's therefore quite fitting that the crew managed to find time to pay homage to one of the most famous scientists of all time.
Astronauts being 'allergic' to Moon dust wasn't something NASA had really planned for. A member of its first group of astronauts had nearly been disqualified from the selection process for his hayfever, but was allowed to continue when he (rightly) pointed out there wasn't exactly any pollen in space. That was that, NASA thought. Or, at least, that was that until 1972, when Jack Schmitt landed on the Moon.
Although Apollo 9 did not travel to the Moon, it still had a very important role to play in the lead up to the first lunar landing. Here are 10 reasons why it deserves more recognition.
Alan Shepard's road to the Moon was not a straightforward one, so you can't blame him for wanting to have a little fun on the lunar surface. He joked in later life that he was probably better known as 'the astronaut who played golf on the Moon' than he was as the first American in space.
Nicknamed 'the Brain', Ed Mitchell was the second ever astronaut to have a PhD. On his way to and from the Moon in 1971, he took part in a psychic experiment designed to see if it was possible to transmit and receive thoughts across tens of thousands of miles.