Apollo 17 Crew Medical Debriefing, 1972

This is the opening segment of the medical debriefing NASA held with the Apollo 17 crew — Gene Cernan, Harrison Schmitt and Ron Evans — at the Manned Spacecraft Center in Houston, days after they returned from the final Apollo Moon landing. It runs a little under an hour, and the subject flagged for PURSUE is the light flash phenomena.

What makes this tape distinct

By Apollo 17 the flashes were no longer a surprise. Earlier crews had reported them, and this mission carried a dedicated experiment to study them. According to NASA’s description, two of the three astronauts said they saw flashes at different stages of the flight — including in orbit around the Moon and while on the lunar surface itself, which extends the observations beyond the coast to and from the Moon.

The description does not say which two crew members, and the recording continues in a second segment, NASA-UAP-D029.

The explanation

NASA describes the effect as now well documented: high-energy cosmic rays passing through the eye strike the retina and are perceived as streaks or flashes. Schmitt’s brief comments in the technical debriefing — near-constant flashes when dark-adapted, but none while blindfolded for the light-flash experiment — show what the crew said on a separate occasion. As with the other NASA light-flash files, this recording is about human vision in space, not about objects outside the spacecraft. For the beginning of the story, see the Apollo 12 medical tape.