Mysterious sounds heard by Nasa astronauts on dark side of the Moon
"Weird music" heard by Apollo 10 astronauts during a trip round the dark side of the Moon in 1969 are getting a mass public airing, after Nasa had shelved the recordings for decades.
The second US spaceship to orbit the Moon, Apollo 10 was the dress rehearsal for Neil Armstrong's famous landing two months later.
Recordings made while Apollo 10 was out of contact around the back of the Moon have been unearthed and will be broadcast on the new series of the Science Channel's Nasa's Unexplained Files, starting in the US this week.
The astronauts on board Apollo 10 can be heard talking about the "weird music" coming through the module's radio and discussing whether they should tell Nasa command.
"You hear that? That whistling sound? Whooooooooo!" one of them says.
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Another voice can be heard saying: "It sounds like, you know, outer space-type music."
"Well, that sure is weird music," one says.
The sound stops after about an hour.
"Boy it got quiet, didn't it?" one of the astronauts says.
The astronauts can be heard saying: "It's unbelievable", "Shall we tell them about it?", "I don't know. We ought to think about it."
According to the Science Channel, Nasa transcribed the tapes "then buries them in the archives without comment".
Then after being declassified, the transcripts had lain in the Nasa archives until 2008.
In a preview of the show, Apollo 15 command module pilot Al Worden explains spacecraft lose contact with Earth for about an hour on the back side of the Moon.
Everything that went on round the back side was recorded, with a data dump being made once the spacecraft was back in contact, so mission control could see what happened.
"If I were to hear something back there, the first thing probably would freak me out," Worden says.
"Nasa would withhold information from the public if it thought it was in the public's best interest."
Planetary scientist Kevin Grazier points out similar sounds were heard by the Cassini spacecraft coming from Saturn. In that case they were caused by charged particles moving through Saturn's magnetic environment.
But Grazier says the Moon doesn't have an atmosphere or a magnetic field, so it would not be expected to be making any transmissions that could be picked up on a radio.
Nasa technicians have theorised the noise was radio interference, but Worden isn't convinced.
According to the Science Channel the origin of the noises mentioned in the Apollo 10 recording remains a mystery.