Brookings Report
The Brookings Report was a report by the Brookings Institute that explained how NASA could conduct its business. It was required knowledge for all mission commanders.
It was approved by the United States House Committee in April 1961. One chapter was titled "Implications of the discovery of extraterrestrial life". When Peri asked if it said to "cut off communications if you find an alien building", Commander Lee Forbes said that was exactly what it said. Brookings discussed incidents of societies on Earth being wiped out by more advanced ones before they were ready.
Knowing about the report, in the early 21st century Commander Forbes shut off communications between Earth and Mars after discovering the "anomaly" there was an artificial alien structure. (AUDIO: Red Dawn)