When we talk about Moon rocks, what do we mean? Not a lunar meteorite. That’s a piece of the Moon that has fallen to earth by natural processes. About 29 such meteorites have been found, including a big one that landed in the Libyan desert in 1999. The fragment now on display in the museum came from that one. Mind you, it didn’t leave the Moon in 1999. In all likelihood, it broke off from the Moon around 4.5 billion years ago, floated around for a while in the vastness of space, got bored and thought, “so what’s Libya’s deal?”
By the way, we know it’s from the Moon because it’s made of the same stuff as Moon rocks. If you think about it, that means we’ve only been able to identify lunar meteorites for a couple of decades, because before the Apollo missions, we actually didn’t know what the Moon was made of. Not completely, anyway.
The only actual Moon rocks humans have are from six Apollo missions between 1969 and 1972, and then trace amounts from unmanned Soviet probes in the ‘70s. We have 842 lbs. in all.
Our rock came from Apollo 15. Astronauts David Scott and James Irwin spent three days on the Moon, rode around in the first lunar rover, and picked up this piece of basalt at a place called Dune Crater. (By the way, you can actually listen to the audio and read the transcripts of Scott and Irwin talking to each other – and Houston – at Dune Crater here.) Astronauts usually photographed rocks in context, using a gnomon for size and color reference, picked them up with tongs, numbered them, and bagged them up.
After the first Moon missions, NASA quarantined rocks (and astronauts) until they could reasonably prove they were safe. This requirement was dropped for Apollo 15, though, since nobody from the earlier missions caught moon madness. Most Moon rocks remain at Johnson Space Center in Houston, where scientists continue to study them. The center’s website offers a virtual tour of its facilities, including cool-sounding places like the Pristine Sample Vault and the Experiment Lab. A few rocks are also held in a remote location in case of a natural disaster in Houston (like that ever happens).
Moon rocks have yielded some important discoveries. We now know the moon and earth are related, having formed from a common reservoir of materials. We know the moon once had a magma ocean. The lack of atmosphere on the moon also means its crust changes very, very little over time. That means we can study Moon rocks to learn about the early evolution of solar system.
Final note: there is a place on JSC’s website where you can request lunar samples for “both destructive and non-destructive analysis in pursuit of new scientific knowledge”. You can also request samples of meteorites, stardust, and cosmic dust, among other things. Good luck on the application, though.