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The far side of the Moon may be less of a mystery than Pink Floyd supposed, especially now we've photographed it, but for the Apollo 10 crew it still pretty spooky; the crew orbiting the planet heard unexplained "outer spacey" music while practising manoeuvres, Nasa has admitted.

The space agency has declassified some of the astronauts' confused conversations as they heard the mysterious sounds, and included it in an upcoming episode of NASA's Unexplained Files.


The three astronauts onboard the mission -- John Young, Eugence Cernan, and Thomas Stafford -- were practicing the separation and docking of the Moon lander and orbiter, as they chatted about the sounds. The transcripts and audio also reveal that they were worried about telling those back on Earth.

The transcripts of the 1969 mission, which were first released in 1998, show how the astronauts reacted; all three astronauts spoke about the music intermittently during the mission, while they were doing other tasks.

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One of Apollo 10's captured views of Earth Nasa

Cernan says: "That music even sounds outer-spacey, doesn't it? You hear that? That whistling sound?" He later describes it as "weird music" and "eerie".

Before the astronauts, who were orbiting the Moon, re-entered the area where they could communicate with ground control they discussed what they had heard. One of the astronauts in the audio recordings says: "Should we tell them about it?" while Stafford expresses doubt "We're going to have to find out about that. Nobody will believe us."


While there's no clarity to what the sounds the astronauts heard, the Unexplained Files series offers some suggestions. The programme posits it may have been radios in the two spacecraft interfering with each-other.

However, Alfred Worden, a Nasa astronaut, is unconvinced by the explanation. "The Apollo 10 crew is very used to the kind of noise they should be hearing. Logic tells me that if there's something recorded on there then there's something there," he told the show.

The three astronauts have never publicly discussed the sounds.