Apollo 17 Crew Medical Debriefing (Continued), 1972
A recording of Apollo 17 astronauts walking through one of the stranger sensory experiences of deep space travel: seeing light that isn't there. The flashes — perceived by two of the three crew members — were caused by cosmic rays passing directly through the eye and triggering the retina, bypassing normal vision entirely. It's a rare first-person account of a phenomenon that was genuinely mysterious in 1972 and is now a known occupational hazard of spaceflight.
This file contains segment 2 of 2 of the Apollo 17 post-mission medical debriefing at the Manned Spacecraft Center (now Johnson Space Center), Houston, Texas. In this continued segment, crew members and debriefers further discuss the “light flash phenomena,” a then novel, now well-documented biological effect where high-energy cosmic rays pass through the eye and strike the retina, causing the perception of light streaks or flashes. Two of the three crew members reported observing these flashes at various points during the mission, including in lunar orbit and while on the lunar surface.