'Space Brain': Mars Explorers May Risk Neural Damage, Study Finds (nbcnews.com)

An anonymous reader quotes a report from NBC News: Astronauts making a years-long voyage to Mars may get bombarded with enough cosmic radiation to seriously damage their brains, researchers reported Monday. The damage might be bad enough to affect memory and, worse, might heighten anxiety, the team at the University of California Irvine said. It's the second study the team has done to show that cosmic radiation causes permanent, and likely untreatable, brain damage. While their experiments involve mice, the brain structures that are damaged are similar, they write in the Nature journal Scientific Reports. NASA knows that astronauts risk physical damage from the radiation encountered in space. Earth is enveloped in a large, protective sheath called the magnetosphere, which deflects a lot of the ionizing radioactive particles that speed through space. Teams aboard the International Space Station are inside that envelope. But moon travelers were not, and this summer a study showed the cosmic radiation may have damaged the hearts of many of the Apollo program astronauts. A trip to Mars would expose astronauts to even more radiation -- enough to cause cancer, for sure, and now this research suggests brain damage, as well. They bombarded mice with the same type of radiation that would be encountered in space, and then looked at what happened to their brains. It did not look good. The changes were seen in the connections between brain cells and in the cells, as well. "Exposure to these particles can lead to a range of potential central nervous system complications that can occur during and persist long after actual space travel -- such as various performance decrements, memory deficits, anxiety, depression and impaired decision-making. Many of these adverse consequences to cognition may continue and progress throughout life."

Comments

This study is garbage

[iris-n]

They didn't expose the rats to anything similar to the radiation an astronaut would be subjected to in their travel to Mars: they fried the rats with a short, intense radiation dose, while the astronauts would be exposed to a low dose long term. In fact, in the study they don't even claim that this radiation is anything similar to what one would find in space, they just say it is "space relevant". So what they found out is only that if you fry rats with radiation it impairs their cognition, and this impairment is long-lasting.

Also, TFS says that Scientific Reports is a Nature journal. This is true, Nature the company (or more precisely Holtzbrinck Publishing Group) does own this journal, but it has nothing to do with the Nature journal, editorially or scientifically. This is just a lame attempt to bestow Nature's reputation on Scientific Reports, which is in fact a pretty crappy journal, that does not even try to select papers based on quality, but claims to check only for correctness.

Re:radiation is the big stumbling block

[Rei]

Not exactly. Ideal shielding is relatively thin metal followed by lots of hydrogen-rich material, plus a small amount of neutron absorbers (boron, etc). The hydrogen-rich material should make up the majority of the mass. This can be hydrogen-rich plastics (such as polyethylene), liquid hydrogen propellant (great ISP, although storage is difficult), methane propellant (what SpaceX plans to use, albeit they don't call for much during coast), ammonia (coolant, easy hydrogen store), water (need it anyway, even easier to store), hydrazine (commonly used for RCS thrusters), etc. NASA has been looking at trying to make structural composite materials out of hydrogenated boron nitride nanotubes, which would be killing two birds with one stone (since they're strong as well).

The reason you need lots of hydrogen is that a lot of your high energy impacts will often kick off neutrons, and these are much harder to block than ionized particles (this is particularly of concern with GCR and high-energy solar flare protons). The best way to eliminate neutrons is to moderate them down to the thermal spectrum so that they can be readily absorbed by high cross section absorbers. Hydrogen is by far the best neutron moderator per unit mass; nothing else really even comes close. It has a fairly high scattering cross section to begin with, and scatters far more per event than other compounds due to its low mass (more energy transfers from the neutron to the hydrogen), and presents far more nuclei to scatter from per unit mass than other elements. Liquid hydrogen is even better because you're thermalizing to a very cold temperature, which dramatically increases absorption cross sections (whether from hydrogen itself, or elements specifically used as absorbers such as boron). But again, liquid hydrogen is more difficult to store than other forms....