Permanent Human Settlement of the Earth, Space and Ocean Frontiers

Saturday, June 03, 2006

Space Radiation's Imminent Threat

There is a position in low earth orbital space over the South Atlantic Ocean and most of South America where the magnetosphere of the earth takes a dip toward the surface of the earth. Into this region is part of the nominal orbits of the space shuttle and the International Space Station. When these manned spacecraft enter this region called the South Atlantic Anomaly (SAA), they fly below a part of the natural space radiation shield and they are exposed to increased levels of space radiation. During these times, astronauts noticed what they first called retinal flashes.
A retinal flash is a streak of light “seen” inside the brain. They are probably erroneously called retinal flashes, because some brain scientists now think they are probably caused by a high energy particle of space radiation streaking through the brain’s neural cortex and killing an optic neuron. A true retinal flash can be caused by mechanical stimulation of the retinal neurons, but these are something else altogether. They were first reported by the astronauts of Apollo 14 on their way to the moon. The flashes were so problematic to astronaut Jerry Linenger on the MIR space station in 1996 that he slept with his head between two lead batteries because the troublesome lights kept his awake when the station orbited though the SAA. He reported that the batteries actually did very little good.
The problem is obvious. If each flash of light represents the death of an optic neuron, then how many other brain cells were killed as the massive, high energy object made its way through the brain to the optic neuron? How many brain cells will be killed in a 1000 day Mars expedition? (Mars has no effective magnetosphere.)
And if all that were not enough worry, we cannot duplicate space radiation on earth. We can only use our most massive particle accelerators to duplicate one to several energetic particles at a time, but nothing like the rich diversity of space born particles. We can only experiment on this with any validity in deep space (outside the influence of the magnetosphere).
The question is obvious: how much is bad and how much is really bad? No one knows. But before we commit astronauts to 1000 days in the celestial shooting gallery, we have to know for sure! We can go ahead and spend our billions inventing space machines to take them there, but until we get a handle on the key question, we will have to know the answer for sure.
Oh, by the way. Since the term retinal flash is not entirely accurate, let me suggest a new name for the flashes caused by space radiation. I suggest we call them the “Tobias Effect”, named after the scientist who first discovered them in 1951 after he placed his head in the beam of the Berkeley particle accelerator. Upon doing so, he reported that his “head was filled with brilliant light flashes” and thought he was seeing into the heart of the universe.
Next time, we’ll examine some possible solutions.