HOUSTON, Oct. 15 -- "I just saw a flash! 100%," Reid Wiseman said inside Orion during the lunar eclipse. About ten minutes later he saw another, and this time Jeremy Hansen had seen it too, a pinpoint of light, "just like a bloop."

The exchange is in NASA's Artemis II Preliminary Lunar Science Report, which counts five distinct impact flashes reported by the crew while the Sun was behind the Moon. Several were seen by more than one astronaut at once. The crew told scientists afterward that they may have seen more, but left any ambiguous flash off the annotated image they sent down.

The detail matters. All five were on the unlit part of the Moon, none were seen in earthshine or sunlight, and NASA's science team called them likely the fai...