NASA's a bit concerned that the rush to the moon created by Google's Lunar X Prize could damage historic sites there.
So it's released its set of guidelines designed to protect such sites, and had them endorsed by the X Prize Foundation.
Now, the 26 teams vying to be the first privately-funded entity to visit the moon will have to take them into account, and their entries will be judged accordingly.
The rules don't, though, have any national or international legal standing.
NASA put together the guidelines using data from previous lunar studies and analysis of the unmanned lander Surveyor 3's samples after Apollo 12 landed nearby in 1969. Experts from the historic, scientific and flight-planning communities also chipped in with the technical recommendations.
The full set of guidelines can be seen here. They cover the Apollo landing site, unmanned landing sites and impact sites, experiments left behind and other signs of human activity such as footprints and Rover tracks.
And the list of artifacts left behind makes fascinating reading, including everything from a cosmic ray detection package to facial wet wipes and a 'defecation collection device'.
The Google Lunar X Prize is promising $30 million total in prizes. First place will go to a privately-funded team that builds a rover which lands successfully on the moon, explores it by moving at least one third of a mile and returns high-definition video and imagery to Earth.
There'll be extra prizes for photographing a Lunar Heritage, Apollo or Surveyor spacecraft site.