While doing some research for an article I am writing, I came across a phenomenon I had never heard about before, despite a lifetime’s interest in all things astronomical. Apparently, astronauts in orbit regularly experience light flashesThis link leads to a long but worthwhile article about these light flashes., most likely caused by cosmic rays decaying in a nuclear reaction as these rays enter the eyeball. In effect, astronaut eyes become human particle detectors. Or that, at least, is currently the leading theory.Another possibility is that the cosmic rays are interacting directly with the part of the brain responsible for vision.

This phenomenon was predicted as early as 1952, and was first experienced by the Apollo 11 mission to the Moon. Ever since, astronauts have reported seeing light flashes while in orbit. Now that a manned Mars mission is on the planning horizon, finding the precise cause of these flashes has become a priority. Currently, the longest period of time that humans have ventured outside the protective sheath of the Earth’s magnetosphere was the 10 days it took to get to the moon and back. A mission to Mars would put humans at the mercy of the vagaries of our Sun for around 3 years, before Mars can offer its protective shieldWe know this thanks to Swedish research..

Space Shuttle and International Space Station (ISS) orbits lie well within the magnetosphere, but even these regularly cross this post’s second bizarre phenomenon, the South Atlantic Anomaly (SAA). The SAA is a region over Brazil, Argentina and the South Atlantic where the magnetosphere is abnormally weak. This weakness is due to the fact that the center of the Earth’s magnetic field is not really aligned with the center of the Earth. The upshot is that cosmic rays tend to reach spacecraft in greater numbers as they fly over the SAA — not surprisingly, the number of light flashes experienced by astronauts increases over this region.

There is a Swedish angle to all this. Sweden’s only prospective astronaut, Christer Fuglesang, is involved in several projects that are trying to get to the bottom of these light flashes. Several particle detectors have been built that wrap around an astronaut’s head, so that if and when s/he sees a light flash, the particle detector tries to capture the precise path of the particle. One such detector has been on Mir since 2002. Another will travel to the International Space Station soon, quite possibly with Fuglesang on his maiden flight aboard STS-116 in 2006 — if Space Shuttle flights resume, that is.