It seems like the kind of strange incident that occurs in a film like Alien or Prometheus.
But it was apparently all too real for Apollo 10 astronauts Eugene Cernan and John Young, who orbited to the far side of the moon in 1970, and heard a strange "whistling sound" that was unlike any sound they had ever heard before.
According to a video posted by the Science Channel on YouTube, the astronauts chose not to brief the National Aeronautics and Space Administration (NASA) about the experience they had for fear of being grounded over concerns for their "state of mind".
As such, their conversation was buried for 40 years until transcripts of the audio recordings were released and made public in 2008.
According to CNN, Michael Collins, who was the first person to fly around the far side of the moon, also recalled hearing "an eerie woo-woo sound" in his book 'Carrying the Fire: An Astronaut's Journey'.
He also added that radio technicians explained to him that that the noise was caused by "interference" when the radio in his colleagues Neil Armstrong and Buzz Aldrin's vehicle was turned on and close to his vehicle.
This was also corroborated by a NASA technician who is interviewed in the video.
The strange noise also stopped after Aldrin and Armstrong's module landed on the moon.
However, most YouTube users seemed to take issue with how the video seemed to making the issue bigger than it is.
This includes user Doug Holmes who asked his "fellow Americans" to "stop making documentaries with a horror movie like vibe. It ruins the credibility of the material".
It turns out the alien conspiracy was only a conspiracy - for now, at least.