Analysis by Ian O'Neill
Space exploration is really bad for our squidgy bodies, but you want to know the worst news? According to new research, it's really, really bad for our squidgy brains too. The high-energy particles that buzz around outside of our protective magnetosphere aren't only a trigger for nasty cancers, they may also trigger certain brain defects, such as Alzheimer's disease.
"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) Department of Neurobiology and Anatomy, in a URMC press release. "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."
And that, my friends, is very bad news if you want to see mankind as a multiplanetary species.
Usually, the human body is protected from the ravages of space radiation as we all live deep inside a thick atmosphere surrounded by an invisible force field -- our global geomagnetic field, the magnetosphere. Highly charged particles generated by the sun and deep space sources (such as supernovae) are deflected and absorbed as they strike our atmosphere.
But for astronauts aboard the space station, they are well above most of the protective layers we enjoy here on Earth, so they live in a higher-radiation environment and have to be warned of solar flare events, for example. But send astronauts further into interplanetary space and they'll be completely on their own, drenched in the most energetic forms of radiation. Although shielding inside spacecraft will be essential, O'Banion URMC team has identified one type of radiation that will be very tricky to shield against.
High-mass, highly-charged (HZE) particles are heavy ions that are generated by supernovae. The most common high-energy particles to be emitted from our sun -- protons -- are low mass and therefore can be relatively easily shielded against. HZEs come in various types, but they are the "bunker busters" of high-energy radiation.
As they carry more mass, they have huge energies and are capable of penetrating the thickest shielding on spacecraft and spacesuits. "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."
For the study, the researchers focused on the impact of energetic iron ions generated by particle collisions at the NASA Space Radiation Laboratory at Brookhaven National Laboratory on Long Island on the brains of mice. Of particular interest was whether the mice experienced neurodegeneration, particularly the biological processes that can trigger Alzheimer's disease.
After the four-legged astronaut analogs were exposed to the equivalent amount of HZEs real astronauts would be exposed to during a hypothetical 3-year mission to Mars, the mice brains' showed signs of the onset of Alzheimer's.
When the mice were tested for their recollection of objects placed in specific locations, the researchers noted significant neurological impairment. Also, physical tracers in their brains signified the onset of the disease -- vascular alterations and accumulations the protein "plaque" associated with afflicted brains.
O'Banion's team has been working with NASA for over 8 years on how radiation effects the central nervous system, complementing the space agency's 25 years of study into how space can be detrimental to astronauts' health.
Does this mean curtains for our interplanetary dreams? Will robots -- with silicon brains and not the "squishy" brains we humans are hindered by -- forever remain our space exploration emissaries? Hopefully not, but it will certainly motivate novel shielding developments and aid crew selection, possibly creating the need for screening processes that will identify individuals with a predisposition to developing the 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."
Source: University of Rochester