A NASA-funded study appearing in the journal PLOS ONE suggests that astronauts on long-duration missions, such as a mission to Mars, could have more to fear than even cancer. The radiation that crews would be exposed to during such a mission could actually accelerate the onset of Alzheimer’s Disease.
Deep space is filled with radiation; we are protected from this radiation by Earth’s magnetic field. Astronauts traveling to distant worlds would have no protection from this threat. Apollo astronauts were fortunate in that their missions only lasted a few days (the longest Apollo lunar mission was Apollo 17, which lasted 12 days, 13 hours, and 52 minutes).
“Galactic cosmic radiation poses a significant threat to future astronauts,” said M. Kerry O’Banion, M.D., Ph.D., a professor in the University of Rochester Medical Center (URMC) Department of Neurobiology and Anatomy and the study’s senior author. “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.”
With enough advanced warning, crews could enter specially protected segments of their spacecraft to avoid one of the most lethal forms of space radiation—solar flares. Currently, however, there is no shielding available for cosmic radiation, which permeates the space environment.
The planet Mars, a destination highlighted as a place where NASA wants to send astronauts to in the 2030s, has no appreciable magnetic field. This means that astronauts would have to closely monitor the amount of time that they spend outside of habitats that would need to be constructed to shield them from the ever-present threat of radiation.
A round trip to Mars could last some three years. NASA also has plans to send astronauts to an asteroid in the early 2020s.
Cosmic radiation exists in low levels—as such the longer that astronauts spend on missions, the greater their exposure.
NASA has been sponsoring studies such as this one for more than 25 years to gain a better grasp of the risks involved. It is hoped that countermeasures to offset the risk involved with deep space missions can be developed.
While NASA has known about the correlation between cancer, cardiovascular, and musculoskeletal issues stemming from long-term exposure to cosmic radiation, the findings of this study of the effects of space radiation on neurodegeneration add an extra dimension to the risks that space flyers face—and one more concern that NASA has to contend with.
The project that O’Banion and his colleagues have been working on is no fly-by-night operation. The team has been studying how the brain’s biological processes could potentially be impacted by cosmic radiation for more than eight years.
Scientists looked into a specific form of radiation: high-mass, high-charged particles, or “HZEs” in particular. HZE particles travel through space at very high rates of speed. According to the study, they are flung across the cosmos by the force of exploding stars. These particles come in a wide range of forms—given this, researchers opted to focus on iron particles.
The selection of iron HZE particles was profound, as other particles created in other environments lack the mass and energy to penetrate the shielding of spacecraft—something the iron particles had no problem doing.
“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.”
NASA decided to have the study conducted at the Brookhaven National Laboratory on Long Island at the agency’s Space Radiation Laboratory. This allowed scientists to take advantage of the facility’s particle accelerators. Researchers smashed various forms of matter together to simulate the dynamics of radioactive particles in space.
Scientists focused on whether or not radiation could speed up various factors that indicate the onset of Alzheimer’s, especially for those subjects with a predisposition of getting the disease. To accomplish this, researchers used mice, which have a well-understood pattern that can be observed as to how the disease impacts these animals over time.
The mice were exposed to various levels of radiation, including those comparable to astronauts on a Mars mission. Afterward, URMC graduate student Jonathan Cherry, who was one of the authors of the study, reviewed the impact of the exposure on the animals. Those mice exposed to Mars-mission levels of radiation were far more likely to fail tests to evaluate their memory. The issues with the mice’s memory appeared far earlier than would normally be the case, indicating that the level of radiation exposure impaired their cognitive abilities.
The mice’s brains also showed signs of vascular alteration, as well as in increase of beta amyloid, which is one of the signatures of Alzheimer’s.
“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.”
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