Astronauts travelling to Mars risk colon cancer and permanently losing the ability to absorb food due to long term exposure to cosmic radiation, warns a new study.
Researchers said current radiation shielding and medicine did not protect humans’ health from long-term exposure from heavy particles during deep space voyages.
The Earth’s magnetic field protects people from the effects of energetic heavy ions such as iron and silicon.
And astronauts on relatively short space journeys such as to the Moon do not get the stomach problems because they are not exposed to the charged particles for long enough.
But the study by scientists at Georgetown University Medical Centre (GUMC) in the US found bombarding mice with the radiation left them with damage to their guts.
The effects to their intestinal “GI function” – thought to be permanent – were not observed in mice under gamma radiation or a control group.
Study senior investigator Doctor Kamal Datta, said: “While short trips, like the times astronauts travelled 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.
“Heavy ions such as iron and silicon are damaging because of their greater mass compared to no-mass photons such as x-rays and gamma (γ)-rays prevalent on earth as well as low mass protons in outer space.
“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.”
Dr Datta’s team found the intestinal cells of mice did not adequately absorb nutrients and formed cancerous growths called polyps after the rodents received heavy ions.
They found evidence that iron radiation caused DNA damage that increased the number of “senescent” cells which damaged their gut’s “GI” functioning.
Dr Datta, an Associate Professor in the Department of Biochemistry and a project leader of the NASA Specialised Centre of Research at GUMC, said: “The cells generate oxidative stress and inflammatory molecules that induce more damage.
“This greatly affected migration of cells that are needed to replace the intestinal lining which slowed down GI functioning.”
He added: “We have documented the effects of deep space radiation on some vital organs, but we believe that similar damage responses may occur in many organs.
“It is important to understand these effects in advance so we can do everything we can to protect our future space travellers.”
The radiation damages a mucous-covered self-renewing tissue found the GI tract found in the intestines, the researchers said.
The top layers of cells are replaced every three to five days with new cells that are transported from flask-like structures beneath the inner surface of the intestines.
Study co-author Dr Albert Fornace said: “Any disturbance of this replacement mechanism leads to malfunctioning of physiologic processes such as nutrient absorption and starts pathologic processes such as cancer.
He added that even though the mice received a low dose over the equivalent of months-long period in deep space, the effects of the heavy ion radiation appeared to be permanent.
The findings were published in the journal Proceedings of the National Academy of Sciences.