Bad news for Mars-bound astronauts – cosmic rays damage your GI tract
In more bad news for future voyagers to Mars, a team of scientists at the Georgetown University Medical Center (GUMC) has found the kind of Galactic Cosmic Radiation (GCR) that astronauts will encounter on long space voyages can cause heavy damage to their gastrointestinal (GI) tract. Using animal tissue bombarded by artificial cosmic ray particles, the researchers found that the radiation produces both immediate and long term health problems.
Decades of investigation into the field of space medicine has revealed that space is much more hostile to the human body than once thought. This is especially true of the hazards posed by prolonged exposure to cosmic radiation during long deep-space missions, such as to the planet Mars.
These hazards include increased risks of cancers such as leukemia, damage to the brain and nervous tissue, as well as general radiation sickness. But now it appears that even the GI tract can be affected, with immediate damage to the digestive system and long term danger of increased cancer risks.
According to the GUMC team, the culprit is heavy cosmic ray ions made of heavy elements like iron and silicon that have been sped up to almost the speed of light. These particles are so heavy and moving so fast that when they strike living cells, they can produce a tremendous amount of damage.
To determine what the effects of these ions would be on astronauts, the team bombarded mice with low doses of iron radiation at the NASA Space Radiation Laboratory (NSRL) in Brookhaven National Laboratory on Long Island, New York. These were then compared to mice that had been exposed to X-rays and a control group that had not been subjected to radiation.
What they found was that the heavy ions had a significant effect on tissues in the GI tract, which is lined with self-renewing tissue with a top layer of mucosal cells. These cells continually renew every three to five days as new cells migrate up from a flask-shaped tissue structure called the crypt. This is a complex, delicate process that the heavy ions can disrupt, leading to both an impaired ability to absorb nutrients and in increased cancer risk.
In addition, the team found that the iron radiation damaged cell DNA, increasing the number of senescent cells, which are unable to divide, and thereby generating oxidative stress and inflammatory molecules in the intestinal tissue.
"With the current shielding technology, it is difficult to protect astronauts from the adverse effects of heavy ion radiation. Although there may be a way to use medicines to counter these effects, no such agent has been developed yet," says Kamal Datta, MD, an associate professor in the Department of Biochemistry and a project leader of the NASA Specialized Center of Research (NSCOR) at GUMC. "While short trips, like the times astronauts traveled to the Moon, may not expose them to this level of damage, the real concern is lasting injury from a long trip, such as a Mars or other deep space missions which would be much longer."
The research was published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).