[Semaphore (OP)]

Quite a lot, accordingly to research reported in SciAm. Mice irradiated with charged particles suffered substantial brain damage which resulted in mental impairment. We can probably forget (pun intended) going to Mars until we can a find a method of shielding the astronauts from the radiation.

[zx16]

But mice have tiny brains.  Whereas human brains are far superior.  Many thousands of times bigger in cerebral volume.

Won't this enable astronauts to safely absorb en-route cosmic radiation, which might knock out a mouse, but won't stop a valiant Mars crew from accomplishing a successful landing?

[Semaphore (OP)]

But mice have tiny brains.  Whereas human brains are far superior.  Many thousands of times bigger in cerebral volume.

Won't this enable astronauts to safely absorb en-route cosmic radiation, which might knock out a mouse, but won't stop a valiant Mars crew from accomplishing a successful landing?

The conclusion of the article was that mice are similar enough to humans to give a good indication that the radiation would be a real problem for a Mars expedition, unless some form of shielding could be found.

[zx16]

Would a helmet made of lead block the cosmic-rays?

[Semaphore (OP)]

Would a helmet made of lead block the cosmic-rays?

I've just re-read the article and it says that lead would work but would be impractical in space because of the weight. I don't have any idea how much lead would be needed, can anyone give an estimate?

[chiralSPO]

First, I don't think brain volume would help. The exposure is probably the result of a uniform bombardment such that each unit of volume gets the same number of hits per unit time. Since a significant portion of the cosmic rays could go right through without interacting I don't think the outer brain would offer any shielding to the inner brain, so the size of the brain will have no effect on the rate. A brain 100 times larger would also get 100 times more radiation.

I think that the amount of lead required to stop cosmic radiation in deep space is quite significant. You could shield the crew with stuff that already needs to come along for a long trip (people have proposed using water for protection).

One could also imagine using a large magnetic field to deflect charged particles just as the Earth's does. One would still need to worry about gamma rays and x-rays (and perhaps to a greater extent: if they are living near a particle accelerator, they can expect bremsstrahlung radiation).

[Semaphore (OP)]

First, I don't think brain volume would help. The exposure is probably the result of a uniform bombardment such that each unit of volume gets the same number of hits per unit time. Since a significant portion of the cosmic rays could go right through without interacting I don't think the outer brain would offer any shielding to the inner brain, so the size of the brain will have no effect on the rate. A brain 100 times larger would also get 100 times more radiation.

I think that the amount of lead required to stop cosmic radiation in deep space is quite significant. You could shield the crew with stuff that already needs to come along for a long trip (people have proposed using water for protection).

One could also imagine using a large magnetic field to deflect charged particles just as the Earth's does. One would still need to worry about gamma rays and x-rays (and perhaps to a greater extent: if they are living near a particle accelerator, they can expect bremsstrahlung radiation).

It was the charged particles that were the major concern.  The authors didn't go into detail about the magnetic field needed, does anyone have any idea how this might work?

[Bored chemist]

But mice have tiny brains.  Whereas human brains are far superior.  Many thousands of times bigger in cerebral volume.

Won't this enable astronauts to safely absorb en-route cosmic radiation, which might knock out a mouse, but won't stop a valiant Mars crew from accomplishing a successful landing?

Let me get this straight; because human brains are a bigger target, and thus easier to hit, you think they are safer

[chris]

This is my write-up of the study that simulated cosmic radiation exposure on brain function:

https://www.thenakedscientists.com/articles/science-news/brain-irradiation-space

[zx16]

Human brains have got vastly more neurons than mouse-brains. Therefore a dose of cosmic radiation which might severely incapacitate a puny mouse-brain, will have only slight effect on a human brain.  The human brain has plenty of reserve capacity.

[Bored chemist]

Human brains have got vastly more neurons than mouse-brains. Therefore a dose of cosmic radiation which might severely incapacitate a puny mouse-brain, will have only slight effect on a human brain.  The human brain has plenty of reserve capacity.

It may have escaped your notice, but human brains have more to do than mouse brains and therefore have less capacity.

Seriously, the unit of dose is the Gray which is based on energy per unit mass.
Since mouse brains are small quite a lot of gammas go through them, but the radiation is more likely to be absorbed by our brains- because they offer a longer path length.

You may like the idea that "Humans are superior- so we will defeat the mice in this (pointless) competition".
Reality doesn't have to agree with your prejudices.