The famous quote marking man's first moon-landing might not be what Neil Armstrong actually said.
It's the mystery of the missing 'a'.
After becoming the first person to set foot on the moon in 1969, Neil Armstrong said what was recorded as: "That's one small step for man; one giant leap for mankind."
But NASA, and the utterer himself, claimed Armstrong actually said, "one small step for 'a' man..." rather than the grammatically incorrect version that was broadcast back on earth.
Even after years of forensic analysis of the audio, professional analysts couldn't find substantial evidence to support Armstrong's claim.
Researchers from Michigan State University (MSU) and Ohio State University (OSU) took a fresh approach to the hunt for the missing 'a' and may have found an alibi to clear Armstrong of his grammatical crime.
The MSU and OSU research team collected 40 audio recordings of conversations between natives of Armstrong’s hometown capital, Ohio, to analyse their pronunciation of 'for' and 'for a'.
Take a listen to the audio and decide for yourself.
The study found 'for a' was commonly blended together to create a 'furruh' sound when pronounced by Ohio natives- much like the sound that can be heard on the original moon-landing audio recording.
MSU assistant professor for communicative sciences and disorders Laura Dilley said the findings, while not conclusive, helped to bolster Neil Armstrong's side of the story.
"We feel we've partially vindicated him. But we'll most likely never know for sure exactly what he said based on the acoustic information," Ms Dilley said.