Follow CBSMIAMI.COM: Facebook | Twitter

MIAMI (CBSMiami) — Two months before Neil Armstrong’s famous 1969 landing, astronauts aboard the Apollo 10 space capsule reported hearing “outer space type” on the far side of the moon.

READ MORE: Hollywood Looks To Tighten Animal Abuse Laws

Recently declassified recordings and transcripts made by NASA of the journey, which took the Apollo 10 capsule out of radio contact range with Earth, show the astronauts reacting with surprise and confusion to an unearthly howling noise in their headsets.

Those recordings will the subject matter of an upcoming “NASA’s Unexplained Files” on the Science Channel.

“It’s about an hour on the backside of the moon, away from Earth where you lose radio contact,” Apollo 15 Command Module Pilot Al Worden said in the episode.

The sound began once the capsule rounded the moon and lost radio contact with Mission Control.

READ MORE: London-Bound American Airlines Flight Returned To MIA After Couple Refused To Wear Masks

“You hear that? That whistling sound? Whooooooooo!,” an astronaut can heard saying on the recording.

Another astronaut says he can: ‘It sounds like, you know, outer space-type music.’

The recordings and transcripts of the sound and the astronauts discussion about it were declassified in 2008.

During the Science Channel episode, experts will look at possible causes for the ‘music’ including a magnetic field or atmosphere interfering with the radio. However, they point out, the moon doesn’t have a magnetic field and there’s not enough atmosphere there to cause such issues.

The source of the noises remain a mystery.

MORE NEWS: Florida COVID-19 Hospitalizations Decrease

Apollo 10 was the fourth manned mission in the Apollo program, and launched on May 18, 1969.