NASA officials overestimated their ability to contain alien microbes after the first moon landing, a new analysis suggests.

I have linked a non-paywall version, but if you can, I suggest checking out the Times version of the story as it goes into much more detail and has lots of great pictures.

Essentially, NASA knew that if there were microbes brought back from the Apollo missions that they had no effective way to contain them. However, to assuage the public, they maintained that their quarantine procedures were effective. This is essentially quarantine theater to aid public perception of the Apollo program.

doi: https://doi.org/10.1086/724888