4 ms·

A little napkin math says the columnar mass of the Martian atmosphere is 18 g/cm^2, versus 10g / cm^2 of aluminum shielding discussed in the paper. So being on

A little napkin math says the columnar mass of the Martian atmosphere is 18 g/cm^2, versus 10g / cm^2 of aluminum shielding discussed in the paper. So being on the Martian surface would probably give you something like 1/10 (atmosphere + planetary mass + environment suit) the heavy ion radiation exposure of deep space. You'd need to be pretty deep underground most of the time (no windows, at least) to be safe for the duration of a reasonable visit. I'll pass!

idlewords 4y ago
The napkin math falls short a bit because the heavy ions that absorb in the atmosphere will create a shower of secondary radiation that reaches the surface. Similarly, heavy ions that hit the surface will create secondary radiation from rock. This factor is why partial shielding in a spacecraft can give the crew a bigger absorbed dose than having no shielding at all.
- JumpCrisscross 4y ago
  Nobody is arguing radiation isn’t a problem on Mars. Just that heavy-ion bombardment per se isn’t something to be concerned with.
  - idlewords 4y ago
    That is not true; the heavy ion component of galactic cosmic radiation in particular is the single biggest risk factor in going to Mars (other than the spacecraft breaking).
    - JumpCrisscross 4y ago
      > galactic cosmic radiation in particular is the single biggest risk factor in going to Mars Sorry, I was unclear. It’s absolutely an issue going to Mars. It isn’t front and centre on Mars.
      - idlewords 4y ago
        It is, though. It's about half as bad on Mars (since the planet physically blocks half the sky) but it remains a showstopper. And trying to shield against it runs you into the problem of getting heavy construction equipment to Mars, plus you run afoul of rules against contamination that we're bound by international treaty to follow, including a ban on digging.
        throwawaytemp29 4y ago
        Lol - let’s have a Mars colony without digging.
        JumpCrisscross 4y ago
        > rules against contamination that we're bound by international treaty to follow, including a ban on digging Is this OST related? Or Mars specific?
        idlewords 4y ago
        It's the Outer Space Treaty as interpreted by COSPAR, which has introduced concepts (like Special Regions) that are unique to Mars. One Special Region is defined as anything more than 5m underground.
  - cnlevy 4y ago
    Actually, there is : https://caseyhandmer.wordpress.com/2019/10/20/omg-space-is-full-of-radiation-and-why-im-not-worried/ https://caseyhandmer.wordpress.com/2019/10/20/omg-space-is-f... It is time we move away from the LNT (Linear No Threshold) radiation risk modeling. See https://en.wikipedia.org/wiki/Ramsar,_Iran#Radioactivity https://en.wikipedia.org/wiki/Ramsar,_Iran#Radioactivity
- ericbarrett 4y ago
  You're right, actually, that means even more exposure than I calculated since even the relativistic ions that are absorbed will still have potential biological effects via the secondary particles. Do you know how to calculate the flux from those?
  - idlewords 4y ago
    This paper looks like a good starting point: https://www.sciencedirect.com/science/article/abs/pii/S221455241730007X https://www.sciencedirect.com/science/article/abs/pii/S22145...

idlewords 4y ago

The napkin math falls short a bit because the heavy ions that absorb in the atmosphere will create a shower of secondary radiation that reaches the surface. Similarly, heavy ions that hit the surface will create secondary radiation from rock. This factor is why partial shielding in a spacecraft can give the crew a bigger absorbed dose than having no shielding at all.

JumpCrisscross 4y ago
Nobody is arguing radiation isn’t a problem on Mars. Just that heavy-ion bombardment per se isn’t something to be concerned with.
- idlewords 4y ago
  That is not true; the heavy ion component of galactic cosmic radiation in particular is the single biggest risk factor in going to Mars (other than the spacecraft breaking).
  - JumpCrisscross 4y ago
    > galactic cosmic radiation in particular is the single biggest risk factor in going to Mars Sorry, I was unclear. It’s absolutely an issue going to Mars. It isn’t front and centre on Mars.
    - idlewords 4y ago
      It is, though. It's about half as bad on Mars (since the planet physically blocks half the sky) but it remains a showstopper. And trying to shield against it runs you into the problem of getting heavy construction equipment to Mars, plus you run afoul of rules against contamination that we're bound by international treaty to follow, including a ban on digging.
      - throwawaytemp29 4y ago
        Lol - let’s have a Mars colony without digging.
      - JumpCrisscross 4y ago
        > rules against contamination that we're bound by international treaty to follow, including a ban on digging Is this OST related? Or Mars specific?
        idlewords 4y ago
        It's the Outer Space Treaty as interpreted by COSPAR, which has introduced concepts (like Special Regions) that are unique to Mars. One Special Region is defined as anything more than 5m underground.
- cnlevy 4y ago
  Actually, there is : https://caseyhandmer.wordpress.com/2019/10/20/omg-space-is-full-of-radiation-and-why-im-not-worried/ https://caseyhandmer.wordpress.com/2019/10/20/omg-space-is-f... It is time we move away from the LNT (Linear No Threshold) radiation risk modeling. See https://en.wikipedia.org/wiki/Ramsar,_Iran#Radioactivity https://en.wikipedia.org/wiki/Ramsar,_Iran#Radioactivity
ericbarrett 4y ago
You're right, actually, that means even more exposure than I calculated since even the relativistic ions that are absorbed will still have potential biological effects via the secondary particles. Do you know how to calculate the flux from those?
- idlewords 4y ago
  This paper looks like a good starting point: https://www.sciencedirect.com/science/article/abs/pii/S221455241730007X https://www.sciencedirect.com/science/article/abs/pii/S22145...