The moon is a rock.

But it's also Selene, Artemis, Diana, Isis, the lunar deities; an eldritch clock by which we measure our growth and fertility; home of an old man in the West and a rabbit in the East; the site of countless imaginary voyages; a long-believed trigger of lunacy (luna...see?). It's another world, close enough to our to peer down at us; to it, we compose sonatas. It can be blue, made of cheese, a harvest moon; we've long fantasized about its dark side, perhaps dotted with black monoliths or inhabited by flying men.

The moon is a totem of great importance in all religions and traditions; in astrology, it stands for all those things which make this fine scienceblogs readership develop facial tics: the unconscious, parapsychology, dreams, imagination, the emotional world, all that is shifting and ephemeral. According to the Penguin Dictionary of Symbols, as the light of the moon is merely a reflection of the light of the sun, "the Moon is the symbol of knowledge acquired through reflection, that is, theoretical or conceptual knowledge."

All of this to say that while the moon is a rock, it's also an idea.

And, as an idea, it appeals to artists. The moon, however, remains beyond the reach of artists by virtue of what makes it interesting to them: namely, its moon-ness, a perfect storm of mystery, opacity, and unreachability.

So just how do you implement the moon in your practice when it's 240,000 miles away? As an artist, how do you stake a claim somewhere inside of the patriotic military-industrial research bureaucracy that controls the purse strings, and thus access to our nearest celestial bodies? There doesn't seem to be a direct entry. If you're part of the original Moon Museum posse, you go in the back door, sneaking your work illicitly onto the heels of a lunar lander. If you're Belgian artist Paul Van Hoeydonck, you meet astronaut David Scott at a dinner party.

Van Hoeydonck is responsible for the only piece of art on the moon, a tiny memorial sculpture called "Fallen Astronaut." The piece is interesting for several reasons. For one, it presents us with a clear understanding of the kinds of technical limitations that moon artists must work under. Limitations, of course, can be instrumental to an artist's practice -- a broke Basquiat painted on window frames and cabinet doors -- but space art's parameters border on the draconian. In the design of the piece, Van Hoeydonck was restricted to materials that were both lightweight and sturdy, as well capable of withstanding extreme temperatures. Since it was to be a memorial to deceased astronauts, it couldn't be identifiably male or female, nor of any ethnic group. The somewhat questionable result: what looks like a metal Lego lying face-down on Mons Hadley.

Like the Moon Museum, Fallen Astronaut was an unofficial venture; the statuette was smuggled aboard the Apollo 15 lunar module by the astronauts themselves -- Scott and Jim Irwin -- without the knowledge of NASA officials. Its "installation" was unorthodox: in laying down the sculpture and its accompanying plaque, Irwin and Scott performed a private ceremony on the lunar surface. "We just thought we'd recognize the guys that made the ultimate contribution," Scott later said. Notable: "the guys" include eight American and six Soviet astronauts, a surprisingly apolitical act of solidarity in the midst of the Cold War.

Scott and Irwin were committed to the sanctity of their memorial; when Scott plopped the piece onto the lunar dust, Irwin covered the act with inane radio chatter to Mission Control, and they didn't announce the memorial until after their return to Earth. Even then, the astronauts kept Van Hoeydonck's name private, hoping to avoid any commercial exploitation of the piece. Van Hoeydonck, undoubtedly hoping to further his career, later violated the unspoken sacredness of Fallen Astronaut by attempting, in 1972, to sell hundreds of signed replicas of the piece at $750 a pop. We'd all recoil in horror if Maya Lin tried the same thing with the Vietnam Veteran's Memorial, but I'm almost tempted to give Van Hoeydonck a pass. After all, the Fallen Astronaut itself is just a totem, and a toylike one at that.

I see this story as something of an inversion of the usual artist-scientist dialectic. Van Hoeydonck, here, was essentially an engineer. All he did was design a tin man to technical specifications, but it was Scott and Irwin who made the visionary decision to perform an unnecessary act of beauty on the chunk of rock orbiting our own. It was the astronauts who snuck the statuette all the way to the moon and secretly installed it. They understood that beyond being a rock, the moon is an idea, and that actions performed on the moon by human beings are instantly imbued with meaning, historical significance, and some kind of indefinable holiness. Scott, Irwin and NASA balked at Van Hoeydonck's commercial enterprise, and the artist eventually retracted it, instead donating various replicas of Fallen Astronaut to museums and keeping the rest to himself, un-monetized.

While it's ordinarily the artists who defend the formal importance of ideas for their own sake, on Apollo 15 it was, well, not the scientists -- but the military-trained, engineer-pilot, non-artist astronauts who did. Which perhaps goes to show that the experience of space, the perspective-altering transcendence of the so-called "overview effect," ultimately turns us all into poets.