Optical connections: Stars in their eyes

'My God, it’s full of stars!’ So reports the startled spaceman, Dave Bowman, when the monolith on a Jovian moon opens to reveal a star gate in the novel and film 2001: A Space Odyssey. But astronauts at least as far back as the Apollo missions have regularly reported a real, if slightly less fantastical, visual phenomenon: strange flashes and streaks of light that are experienced even with the eyes closed, of a type that is not normally detectable on Earth.

Buzz Aldrin recalled seeing such entoptic phenomena, or phosphenes, on the 1969 Apollo 11 mission, the first to land on the Moon. The crew of Apollo 14, when 100,000 miles into their 1971 lunar journey, also noted these flashes of light which were especially evident during scheduled sleep periods and in the darker recesses of the spacecraft. NASA, suspecting that the source of the phosphene phenomenon was probably cosmic radiation, developed the Biostack experiment that was carried on Apollo missions 16 and 17. The apparatus comprised specimens of bacteria, crustaceans and insects at different stages of development sandwiched between specially prepared photographic plates to both record the radiation and its effect on the biological subjects.