Radiation encountered on extended trips to the Moon or Mars could harm astronauts鈥� brains, experiments on rats suggest. The space farers could face problems with spatial learning, memory and stress.
Astronauts aboard the space shuttle and the International Space Station are largely protected from space radiation by the Earth鈥檚 magnetic field. But the crew of a mission to Mars could spend three years outside this protective bubble.
So NASA recently awarded funding for 12 projects that will investigate how long-term radiation exposure in interplanetary space could potentially cause health problems in astronauts.
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One award will help continue studies of how radiation affects the behaviour and cognitive abilities of rats. It is led by Bernard Rabin of the University of Maryland in Baltimore, US.
Rabin鈥檚 work over the past several years has already shown worrisome effects. He has been focusing on the effects of heavy particle radiation, which is made up of fast-moving nuclei from heavy elements like iron.
These are more difficult to shield against than lighter elements, and Rabin鈥檚 studies suggest that they are more potent in affecting the brain. The team beams heavy particles into the brains of rats using particle accelerators, then tests the rats to see how the radiation affects their cognitive abilities.
Rats whose brains have been exposed to heavy particle radiation perform more poorly in navigating mazes and have a harder time learning to press a button to get a food pellet. They also are more easily distracted and experience more anxiety in stressful situations.
Juice cocktail
The effects are apparent in rats given as little as 0.5 gray of radiation, which is small enough that the rats live out their normal lifespan. That amount is comparable to the levels that astronauts would face on a Mars mission, Rabin says. He notes, however, that the radiation is delivered to the rats in one brief burst, whereas the astronauts鈥� exposure would be spread out over several years 鈥� a difference that could potentially affect the results.
Still, the radiation could impair astronauts鈥� abilities on these long-duration missions. 鈥淚f you鈥檝e got to locate an object in space and you can鈥檛, that presents some problems,鈥� Rabin told New 杏吧原创.
Changes in the astronauts鈥� response to stress might also cause problems, he says: 鈥淚f there鈥檚 an increase in the level of anxiety, for example, the astronauts are not going to be willing to explore as much. Or if there鈥檚 a decrease in anxiety, they might be taking chances that aren鈥檛 wise.鈥�
It may be possible to develop an antidote for the radiation, however. One of Rabin鈥檚 studies showed that rats given strawberry and blueberry extracts before being irradiated were less prone to its harmful effects.
This could be because the extracts contain antioxidants. Researchers still do not know exactly how heavy particle radiation creates cognitive problems, but it is known to create highly reactive oxygen-containing molecules in the body.
Mission design
So-called reactive oxygen species are suspected as a contributor to the ageing process. As it turns out, the problems the rats encounter from radiation exposure are very similar to those that ageing rats experience, Rabin says.
The new phase of Rabin鈥檚 studies, which he hopes to begin in January 2007, will further explore the attention deficit effects from radiation and will look for effects on the rats鈥� ability to remember objects they have seen before. The studies will also look for changes in gene expression in the rats鈥� cells.
The new research will be carried out at the NASA Space Radiation Laboratory, part of the Brookhaven National Laboratory in Upton, New York, US.
Other studies in the new set of NASA-funded projects will look into the effects of radiation on signalling between nerve cells and investigate the details of how speeding particles do their damage in the brain.
Jay Buckey, a doctor who flew aboard the space shuttle in 1998 and currently works at Dartmouth College in Hanover, New Hampshire, US, says a lot more research needs to be done to understand how cosmic radiation affects the brain, and at what exposure level problems will appear.
鈥淚 think that is very important for long-duration spaceflight,鈥� he told New 杏吧原创. 鈥淥nce you know how much radiation is acceptable, you can design the mission and spacecraft to keep within those limits,鈥� he says.
