Orbiting astronaut sees mystery lights
Astronaut Ed Lu returned on Monday from a six-month tour as science officer on the international space station with loads of memories and at least one nagging puzzle: what caused the mysterious flashes of light he saw while studying the Earth's aurora from orbit?
Lu, who was a research astrophysicist before becoming an astronaut in 1994, estimates that he spent 100 hours watching the northern and southern lights during half a year n space. The auroral light show, which takes place well below the station's 380km altitude, shimmers and pulses depending on natural variations in incoming solar particles trapped by the Earth's magnetic field.
On three occasions - July 11, September 24 and October 12 - Lu saw something markedly different: flashes as bright as the brightest stars, which lasted only a second then blinked off again. In one instance, he called crew-mate Yuri Malenchenko over to the window to see the bursts. Lu says they appeared very different from the random but harmless retinal flashes that many astronauts experience when heavy cosmic rays hit their eyeballs.
Given his limited time and ability to research the problem in space, Lu has tried to rule out other obvious explanations. The flashes weren't like sun glint from dust particles outside the station, which rotate and last longer than a second. Nor were they meteors, which look like linear streaks. Viewing conditions were wrong for a satellite or other artificial object. They only appeared in the direction of the aurora. And Lu checked weather maps, which showed no lightning storms below at the time of his observations. All of which leads him to the tentative conclusion that he saw some previously unreported pheno-menon associated with the aurora.