Permanent Human Settlement of the Earth, Space and Ocean Frontiers

Friday, June 02, 2006

The Great Unknown of Space Radiation

Humanity has announced its full intentions to go to Mars. With our current technology, such a trip will require about 1000 days. But, that is an audacious announcement, considering very few men have ascended above the protective environment of the Van Allen Radiation belts for any significant length of time. Even the US and Russian space stations have all orbited beneath that protection, so there is not much information on what happens when a human exposes their brain and body to raw, unfiltered space radiation.
Now, it is true that the Apollo Astronauts all traveled well out of the belts to the Moon and back for periods of more than a week. But how does 10 days compare to 1000? How much damage can 1000 days exposure to raw space radiation do to the soft human tissues and especially to difficult to regenerate brain neurons?
The answer is – no one knows.
Radiation is not radiation is not radiation. A medical or dental x-ray will penetrate your flesh with a photon – electron particle zipping along at nearly light speed. But it is quite small – say 1/1836 of a single atomic mass unit. So when the x-ray is over, so what? It hurts far less than paying the bill. And if you could look deep into your cells, you almost certainly would notice nothing amiss. It is theoretically possible that the tiny particle traveling with an energy of kilo-volts may have detached one or two DNA bonds, but they probably repaired themselves immediately or they were in non-reproducing cells and it did not matter. The end result is the same billions of times every day – no harm no foul.
But in space, the monsters are MUCH bigger. Obviously the earth is “in space” but we don’t get visited by many of the big monsters. Most of them strike the Van Allen radiation belts and the big guys are shunted up and reflected/deflected away from us. Thanks to the earth’s natural magnetic fields, we don’t get hit very much.
But let’s compare cosmic radiation with x-rays or natural occurring radiation sources such as radium or uranium. Again, they are small – in the thousands of electron volt ranges. But space radiation sources were generated in the heart of stars and supernovas. These particles are NOT lowly electrons of the 1/1836 AMU variety – they are of 1 or greater AMU masses (nearly two thousand times more massive) and they are also traveling at relativistic velocities near the speed of light. The end result is, instead of a momentum of a few thousand electron volts, the monster carries an energy measured in the billions of electron volts for each one. Further, instead of sub-sub-microscopic effects, its linear energy transfer trail (LET) is so large it can actually be viewed with a microscope where it passed thorugh the cell's tissues!
What happens when one of these monsters strikes your cells or your neurons? Well, the answer is relatively simple: its’ lights out. More tomorrow…