The Georgetown University Medical Center (GUMC) research team has been using animal models to simulate the radiation exposure of astronauts heading to Mars. They found that GCR levels expected throughout the trip can inflict severe harm upon gastrointestinal tissue.
Now they are worried that prolonged exposure to GCR will lead to higher chances of stomach and colon cancers. An earlier work of theirs already tackled other potential health risks from exposure to highly charged heavy ions found in deep space. They reported that astronauts would suffer possible brain damage and faster aging during the planned trips.
The magnetosphere of Earth protected humans from these heavy ions. However, even the best and thickest shielding used aboard manned spacecraft cannot repel energized particles of that magnitude. (Related: Microgravity and radiation: Astronauts headed to Mars will face many health challenges.)
GUMC senior researcher Kamal Datta explained that the greater the mass of an ion, the more damage they can inflict upon living tissue. So X-rays and gamma rays on Earth would not do that much damage to humans, but iron and silicon ions in deep space will hurt.
The best shielding technology available is not enough against this heavy ion radiation. There are also no pharmaceutical drugs that can protect against the harmful effects of this bombardment.
Shorter trips to nearby locations – such as the Moon – are safer. Any damage to living tissue will be reduced due to the limited extent of exposure. However, a deep space mission to Mars or an asteroid could result in permanent damage.
The GI tract is particularly weak toward this kind of radiation. The tissue of this organ constantly renews itself through cell division and proliferation. It sheds its uppermost layer of cells every three to five days. Replacement mucosal cells are produced by the crypt, a flask-like organ deep within the gut.
"Any disturbance of this replacement mechanism leads to malfunctioning of physiologic processes such as nutrient absorption and starts pathologic processes such as cancer," explains Datta's co-author and fellow GUMC researcher, Albert Fornace Jr.
Fornace, Datta, and their teammates used a mouse model to simulate the effect of heavy ions on the human GI tract. A group of animals was doused with iron radiation. The small intestines of these heavy ion-exposed mice were compared with those from two other groups: A healthy control group and another group that got bombarded with gamma rays.
The intestinal tissue of the mice in the heavy ion group were badly damaged by GCR. The small intestine could not absorb enough nutrients from digested food. It also developed tumorous polyps.
Furthermore, the GUMC researchers reported that the heavy ion radiation damaged the DNA of the mice. The genetic damage led to the proliferation of senescent cells that are unable to divide and reproduce.
These senescent cells trigger inflammation in the GI tissue that aggravates the earlier damage. The inflammation also stops new mucosal cells from moving to the intestinal lining, causing further dysfunction.
The worst part is that any harm caused by heavy ion radiation cannot be undone. Astronauts exposed to galactic cosmic radiation for too long may end up with cancerous growth in their gut as well as their brain.
Learn more about the perils of deep space travel at Cosmic.news.