Space music: Nasa releases recordings of strange sounds heard by Apollo 10 astronauts

Nasa has released recordings of "space music" heard by astronauts as they orbited the moon, but buried by the US space agency for nearly 50 years.

The uncanny whistling sounds were experienced by astronauts on the 1968 Apollo 10 mission as their shuttle passed across the far side of the moon, out of radio contact.

Astronauts Thomas Stafford, John Young and Eugene Cernan recorded the sounds and transmitted them to mission control in Houston.

Transcripts of conversations on board the flight - originally marked as confidential, but released in 2008 - appear to show the three men experienced something they could not explain.

"Did you hear that whistling sound too?" Stafford, the flight commander, asks.

"Yes. Sounds like - you know, outer-space type music," replies Cernan.

Now the recording of the sound has been made public.

According to 'NASA's Unexplained Files', a new series on the US Science Channel, the astronauts were reluctant to mention the sounds to their superiors for fear they would be deemed unfit for future missions.

But while the show makes much of the "space music" - as well as the fact that Nasa apparently failed to disclose it - sceptics say the sounds were likely just a technical glitch.

A statement from Nasa quotes Cernan himself suggesting the recording was "probably just radio interference".

"I don't remember that incident exciting me enough to take it seriously," he was quoted as saying.

Nasa's Apollo programme consisted of 12 manned missions, launched in the 1960s and early 1970s.