The NASA-funded study assessed how cosmic radiation would impact the astronauts throughout their trip in deep space. The effect of cosmic radiation on the human body has been a concern for the US space agency as it plans manned missions into deep space, such as one to a distant asteroid in 2021, and another to Mars in 2035.
Earth’s magnetic field usually keeps us, and those in low Earth orbit, safe from the perils of cosmic radiation. However, beyond Earth’s protective magnetic fields, space travelers are exposed to a constant barrage of radiation.
With adequate warning, such as in the case of solar flares, steps can be taken to protect astronauts from dangerous forms of radiation. However, other forms of cosmic radiation, which occur without warning, cannot be blocked as effectively.
“Galactic cosmic radiation poses a significant threat to future astronauts,” said M. Kerry O’Banion, a professor in the University of Rochester Medical Center (URMC) and senior author of the study. “The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognized. However, this study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with Alzheimer’s disease.”
In the past, scientists studied the impact of cosmic radiation on a living being’s cardiovascular and musculoskeletal systems, as well as potential risks of contracting various forms of cancer.But the new study, published in PLOS ONE, examined the possible effects of space radiation on neurodegeneration, a gradual loss of brain structure or function.
For this study, researchers wanted to find out what role, if any, cosmic radiation plays in accelerating the biological and cognitive indicators of Alzheimer’s disease, especially in those predisposed to developing the illness.
They specifically wanted to learn more about the impact of radiation from high-mass, high-charged (HZE) particles, which come in many forms and travel through space with the force of exploding stars.
Instead of examining hydrogen protons, which are produced by solar flares, the researchers decided to study iron particles. They say HZE particles, such as iron, when combined with their high rate of speed, are able to go through solid objects, like a spacecraft’s walls and protective shielding.
“Because iron particles pack a bigger wallop, it is extremely difficult, from an engineering perspective, to effectively shield against them,” said O’Banion. “One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.”
The researchers exposed mice to various doses of radiation, including levels that would be similar to what astronauts would experience during deep space voyages.To evaluate the cognitive and biological impact of the radiation exposure, the mice were then put through a series of experiments in which they had to recall objects or specific locations. Researchers observed that the radiation- exposed mice were much more likely to fail these tests, suggesting neurological impairment, earlier than the symptoms would typically appear.
Along with symptoms of neurological damage, the researchers found that the mice’s brains also showed signs of vascular changes and had a greater than usual buildup of beta amyloid, the protein “plaque” that gathers in the brain and is one of the characteristics of Alzheimer’s Disease.
“These findings clearly suggest that exposure to radiation in space has the potential to accelerate the development of Alzheimer’s disease,” said O’Banion. “This is yet another factor that NASA, which is clearly concerned about the health risks to its astronauts, will need to take into account as it plans future missions.”