Image: Cosmic rays
J. Yang / NSF
Little is know about the ultra high-energy cosmic rays that regularly penetrate the atmosphere.
updated 12/31/2012 8:42:03 PM ET 2013-01-01T01:42:03

Radiation in space might harm the brains of astronauts in deep space by accelerating the development of Alzheimer's disease, a new study on mice suggests.

The research reveals another risk that manned deep-space missions to places such as Mars or the asteroids could pose, scientists added.

"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," study author Kerry O'Banion, a neuroscientist at the University of Rochester Medical Center, said in a statement.

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Space is filled with radiation that can harm people. While Earth's magnetic field generally protects the planet, once astronauts venture beyond low-Earth orbit, they are constantly bombarded by a shower of dangerous particles known as cosmic rays. The longer an astronaut is in deep space, the greater the risk, which is especially of concern given NASA plans for manned missions to an asteroid in 2025 and to Mars by about 2035 — the round trip to the Red Planet alone could take at least two years.

For more than 25 years, NASA has funded studies to see what the potential dangers of space travel might be. For instance, past research analyzed the potential impact of cosmic rays on the risk for cancer and potential problems with the cardiovascular or musculoskeletal systems.

Now scientists have for the first time examined the effects space radiation might have on neurodegeneration — in particular, the biological processes in the brain linked with the development of Alzheimer's disease, which typically involves progressive mental decline over several years. They found "galactic cosmic radiation poses a significant threat to future astronauts," O'Banion said. [ Inside the Brain: Photo Journey Through Time ]

Perils of space radiation
O'Banion and his colleaguesinvestigated a specific kind of space radiation known as high-mass, high-charged (or HZE) particles. These particles zip through space at very high speeds, likely the result of exploding stars and other deep-space catastrophes from elsewhere in the galaxy. Unlike cosmic rays consisting just of hydrogen nuclei, which solar flares generate, the mass and speed of HZE particles allow them to punch through solid objects such as a spacecraft, or any astronauts inside.

"Because iron particles pack a bigger wallop, it is extremely difficult from an engineering perspective to effectively shield against them," O'Banion said. "One would have to essentially wrap a spacecraft in a 6-foot block of lead or concrete."

The scientists focused on the impact of iron HZE particles generated by particle accelerators at the NASA Space Radiation Laboratory at Brookhaven National Laboratory in New York. Mice were dosed throughout their body with levels of radiation comparable to what astronauts might receive during a mission to Mars.

The mental function of the mice was tested with a series of experiments — for instance, they had to recognize places linked with unpleasant electric shocks to their feet — and rodents dosed with radiation were far more likely to fail at these tasks. The brains of the mice also showed signs of inflamed blood vessels, and possessed abnormally high levels of beta amyloid, a protein that accumulates as one of the hallmarks 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," O'Banion said. "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."

Space radiation vs. astronaut
It remains uncertain why these HZE particles might have this effect on the brain.

"This is, of course, the $10 million question," O'Banion told The fact the researchers saw a blood vessel response, but not clear evidence of brain inflammation "suggests the possibility that the radiation effects are actually in the body of the mice, and that changes there might be affecting amyloid deposition."

O'Banion did caution "we gave the radiation all at once — the mice experienced over a few minutes what astronauts will experience over three years. We have no idea whether the biological effects of HZE particles will be the same when given at low dose rates. Many would argue that ours is a worse-case scenario, and that the changes are likely to be entirely different since the body might adapt to small chronic dosing."

In the future, O'Banion and his colleagues will examine the effects the brain experiences from exposure to radiation elsewhere in the body. They also plan to see whether space radiation might influence development of Parkinson's disease.

"I would add that there are at least three other laboratories pursuing similar studies," O'Banion said. "The nice thing about this is that we will soon know if our results hold up in other labs."

The scientists detailed their findings online Dec. 31 in the journal PLOS ONE.

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Photos: Month in Space: January 2014

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    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
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    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
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    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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