'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

Not only a travel problem

[manu0601]

Once travelers get to mars the problem is not over, as Mars magnetic field is rather weak, because its dynamo was killed a long time ago

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]

Indeed, most plans call for varying materials - and not just with respect to the inside/outside, but also with where they are on the spacecraft. Even the passengers' own bodies act as shielding for other other passengers and needs to be taken into account. Modeling radiation and health risks on interplanetary missions is not a simple task!

If anyone wants to get more of a sense of how cross sections of different elements / isotopes can vary with different types and energies of radiation, I strongly recommend the Sigma server. Start off with neutrons (although you can change that in the dropdown on the top right), pick an isotope, then look at the options on the right. You'll see lots of entries of the form (n, X). The first part in the parentheses is what the incoming particle is; the second part is what the heaviest outgoing particles are. (n,gamma) for example means that there are no nucleons that result from the collision, only gamma; this is a simple neutron-capture transmutation. (n, total) means the total of all cross sections; (n, elastic) is elastic scattering (the dominant method of moderation at low energies; follows the same sort of energy/angular momentum distribution as elastic collisions between objects on macroscopic scales); (n, inelastic) is inelastic scattering (an additional loss mechanism at high energies where the particle is absorbed and then re-emitted, with a more complex energy distribution), etc. Click on "plot" for any category and it'll show you the result.

For example, here's the (n,alpha) for 10B, a well known neutron absorber. And indeed, these are very high cross sections compared to, say, the odds of elemental carbon doing anything to get rid of the neutron. But note how vastly higher the cross sections are in the thermal (meV) spectrum than they are in the fast (MeV) spectrum. Even with boron, you're unlikely to capture fast neutrons (MeV range or higher) except with a great thickness of absorber. But if you moderate them down - moderation having a high cross section - then they become easy to capture. Remember when looking at these charts that 1H is also 1/10th the molar mass of 10B.

On the other hand, low-Z (light) materials aren't that great at blocking certain types of radiation - if you want to block EM radiation spectrum, for example, you want high-Z materials (that's why there's the standard "lead apron" for getting an x-ray). But the balance of effects in space turns out to favor the need for low-Z materials.

If the terms above like "cross sections" are unfamiliar... picture a particle of any type of radiation like a baseball pitched randomly toward an area where someone has hung a bunch of spheres. What's the odds that the baseball is going to hit one of them? Well, it depends on the cross section that they present to the ball. While a naive expectation might be that it would just simply be proportional to the size of the atoms, in practice different isotopes vary widely in their different effective cross sections to different particles and different reactions. Still, cross sections are measured in "barns", which is a unit scaled to be roughly the size of typical atomic physical cross sections for comparison purposes. Anyway, you can just read nuclear cross sections as "how likely a reaction is per unit traveled through the target".

Oh, and I forgot to mention one other thing: when picking shielding materials, neutron capture or other transmutation reactions alter the isotope that they hit. Often what they produce will be unstable and will decay - sometimes multiple times - releasing more radiation. So it's also important to look