NASA recently released evidence buried for decades showing that astronauts on the Apollo 10 lunar mission in 1969 heard strange "space music" that seemingly defies explanation – or did it ... and does it? Many news services have picked up on the story and claim that the "space music" incident is only now being made public, but NASA disagrees. According to the space agency, the audio and transcripts from the mission have been available in the National Archives since 1973 and the explanation of the event is quite down to Earth.

The Science Channel's speculative program NASA's Unexplained Files recently aired a story claiming that when the Apollo mission was on the far side of the Moon and out of radio contact with Earth, the crew heard weird electronic sounds that were described by Lunar Module Pilot Eugene Cernan as "outer-space-type music." The narration of the segment puts a lot of emphasis on the "out of contact" angle – hinting that "something" exciting and exotic might have been behind the strange sound. Aliens, perhaps?

The segment then goes on to claim that the information was only released in 2008, implying that the evidence of the incident was suppressed by the US government for decades, and that the astronauts themselves feared to talk about the incident. These assertions were subsequently picked up and repeated by many major news services.

However, NASA disagrees with the Science Channel's account and in a statement released today says that though the tape recordings and transcripts of astronaut conversations were marked Classified in 1969 as a matter of standard security, the audio and transcripts were made public in 1973 and deposited in the National Archives. The agency also says that, though the incident was well known in radio and space circles, the only new releases regarding the "space music" incident have been digital files that can be streamed over the internet.

In addition, astronaut Cernan said on Monday that the crew didn't regard the incident as at all significant.

Lunar Module Pilot Eugene Cernan NASA

"I don't remember that incident exciting me enough to take it seriously. It was probably just radio interference," said Cernan. "Had we thought it was something other than that we would have briefed everyone after the flight. We never gave it another thought."

The transcript from Apollo 10 record the conversation of the astronauts regarding whooing and whooping sounds coming from the radio equipment while the crew carried out various tasks. Below are the relevant segments with time stamps in mission day, hour, minute, and second, and the speakers identified as Commander Thomas Stafford (CDR), Command Module Pilot John Young (CMP), and Lunar Module Pilot Eugene Cernan (LMP).

04 06 13 02 LMP That music even sounds outer-spacey, doesn't it? You hear that? That whistling sound?

04 06 13 06 CDR Yes.

04 06 13 07 LMP Whooooooo. Say your –

04 06 13 12 CMP Did you hear that whistling sound, too?

04 06 13 14 LMP Yes. Sounds like – you know, outer-space-type music.

04 06 13 18 CMP I wonder what it is.

...

04 06 17 58 LMP Boy, that sure is weird music.

04 06 18 01 CMP We're going to have to find out about that. Nobody will believe us.

04 06 18 07 LMP Yes. It's a whistling, you know, like an outerspace-type thing.

04 06 18 10 CMP Yes... VHF-A ...

04 06 18 16 LMP Yes. I wouldn't believe there's anyone out there.

VHF-A refers to a radio system aboard the spacecraft and points to the cause of the odd sounds. Writing in Air and Space, Paul D. Spudis of the Lunar and Planetary Institute in Houston, Texas, says that Apollo carried many radio links for voice, telemetry, navigation, biomedical data, and other information.

Earth as seen from Apollo 10 NASA

These complex systems had tendency to interfere with one another and similar noises were reported on other missions, such as by Apollo 11 Command Module Pilot Michael Collins. In this case, the most likely culprit was interference from the Lunar Module and Command Service Module Very High Frequency VHF transmitters.

Spudis went on to point out that the reason these sounds weren't heard often or consistently is because not all radio links were active simultaneously and each Apollo spacecraft differed slightly from one another in design and construction. In addition, Apollo 10 was in a peculiar position because, unlike Apollo 8, it was the first circumlunar mission to carry the Lunar Module.

This also explains the mild surprise shown by the crew, despite being experienced astronauts well-acquainted with their radio equipment. Space is a stressful and very alien environment that it's very difficult to simulate. Accounts by many astronauts relate how they found the real thing very different from training.

The crew of Apollo 10 NASA

So while alien space music wasn't part of the equation, the real achievements of the Apollo 10 are worth recapping. Launched on May 18, 1969, it was the fourth manned Apollo mission and the second manned mission to orbit the Moon. As mentioned, it was also the first lunar mission to carry the Lunar Module, which the crew used in orbital tests as a rehearsal for Apollo 11. So detailed were these tests that the fuel tanks were deliberately kept only partly filled so the LEM crew wouldn't be tempted to actually land on the Moon.

Apollo ten racked up a string of records during its flight. It was the fastest manned vehicle in history with a top speed of 39,897 km/h (11.08 km/s or 24,791 mph) while returning to Earth, the highest altitude of a manned flight at 408,950 km (220,820 nmi). the first of two Apollo missions with an all-experienced crew, and the only Apollo crew whose members flew on subsequent missions.

Source: NASA