Twelve astronauts have been on the surface of the Moon. On it, they’ve left behind some American flags, some equipment, golf balls, a small statuette to commemorate fallen astronauts, and some other, er, artifacts.

Among the things the astronauts left to lighten the load for the return trips were their “defecation collection devices,” also known as emesis bags (top). So decades-old containers filled with decades-old astronaut turds are still hanging out on the Moon.

In addition to the cool-gross factor, this astro-poop has some scientific and, with the other artifacts up there, cultural value. Some astrobiologists are interested in how bacteria in the abandoned feces have fared, and some anthropologists and historians would like to see the moon landing sites and all the artifacts there protected as part of a World Heritage Site.

For now, NASA doesn’t appear to have any plans to actively preserve the site, but with commercial space flights on the horizon, they have set some guidelines to keep any future space tourists from messing with their stuff. They’ve established buffer zones and minimum distances from the Apollo artifacts that Moon visitors should maintain, varying from just over half a mile to a little over a mile. Visiting spacecraft are also advised to land and take off at least one and a quarter miles from the historic sites. Stepping in poop, after all, is a sure way to ruin your space vacation.