Mercury Atlas 9 Audio Excerpt, May 15, 1963

Approximately one hour and 41 minutes into the final and longest flight of Project Mercury, Mercury-Atlas 9 mission (MA-9) Faith 7 Pilot L. Gordon Cooper Jr. notes that he sees “John’s fireflies,” referring to John Glenn’s term from the Mercury-Atlas 6 mission. NASA later determined that the “fireflies” are attributable to frozen condensation separating from the spacecraft body. The white, green-hued appearance of this phenomenon results from sunlight reflecting off frozen condensation.