Nasa has asked any future visitors to the Moon to keep away from the Apollo landing sites out of respect for history.
There are 26 teams and private companies currently competing for the $20m Google Lunar X Prize, to be awarded to the first private group to land on the Moon.
With all that traffic coming to the Moon, Nasa is taking steps to protect its past.
It has told the X Prize competitors, whose task is to land a probe on the lunar suface, travel a third of a mile and send back an HD photograph, to stay at least 1.2 miles away from the Apollo sites and 1,600 feet from the Ranger impact sites.
Nasa said in a report, written in 2011 but posted recently on its website, that the sites are important to mankind and had to be protected.
"The guidelines do not represent mandatory US or international requirements," it said.
"Nasa provided them to help lunar mission planners preserve and protect historic lunar artefacts and potential science opportunities for future missions."
"Nasa and the next generation of lunar explorers share a common interest in preserving humanity's first steps on another celestial body and protecting ongoing science from the potentially damaging effects of nearby landers."
The Google Lunar X Prize awards more money - up to $4m - for any company that takes a photo of a man-made object on the moon.
But Nasa has asked that teams try and avoid the Apollo 11 and 17 sites, which were the first and last places that man walked on the Moon.
Nasa reportedly worked with the private companies looking to land on the Moon before releasing its report .
"Only one misstep could forever damage this priceless human treasure," the report said.Suggest a correction