5 ms·

Gonna have to figure out how to deal with relativistic iron nuclei: https://pubmed.ncbi.nlm.nih.gov/11540033/ https://pubmed.ncbi.nlm.nih.gov/11540033/

JumpCrisscross 4y ago
> relativistic iron nuclei The Martian atmosphere is 1/166th the density of Earth's [1]. At the ISS's altitude, it's something like a trillionth. [1] https://en.wikipedia.org/wiki/Atmosphere_of_Mars https://en.wikipedia.org/wiki/Atmosphere_of_Mars
- idlewords 4y ago
  The Martian atmosphere does not provide meaningful shielding against heavy ion radiation unless you're way down in the Hellas basin (where no one particularly wants to land). You reduce the flux by half compared to deep space just by having a big rock blocking half of the sky, but you'll still get all the cancer sooner than later.
  - ericbarrett 4y ago
    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?
  - mlindner 4y ago
    The Martian atmosphere may not but the surface of the planet does, cutting half the yearly dose versus being in deep space. And I'm not sure I buy the argument that the atmosphere provides little protection. There's a lot of atmosphere there still, enough you can push down on it and rise into the sky if you have some carbon fiber blades moving at very high speeds. I'd think a iron nuclei would hit a lot of atoms on the way down. > you'll still get all the cancer sooner than later. Cancer risk from radiation is probabilistic. If you spend all day outdoors then you increase your lifetime risk of cancer by a significant degree, but it's not like you're definitely going to get cancer. Additionally, most habitation modules, at least early on, are planned to be buried in martian regolith. Also the moon is worse than Mars in all respects with regard to this so you're effectively arguing that humans should never leave the orbit of Earth. I'm not a fan of that future. (BTW, we deal with much higher radiation levels in hot cells in reactors here on Earth, and those even have windows into them. I'm sure we can work out something.)
    - idlewords 4y ago
      You don't have to buy the argument; you can look up the scientific papers. Heavy ion radiation is hard to shield against and creates high energy secondary radiation when it hits air, metal, or rock. Moreover, there is strong evidence cancer risk from heavy ions is considerably greater than predicted by the absorbed dose model we use for other kinds of ionizing radiation. Search on "non targeted effects heavy ions" to read up on this; it's a fascinating topic. The upper error bar right now for a 1000 day Mars mission is upwards of 20% risk of radiation-induced death; most of this is from the heavy ion component of cosmic rays.
      - mlindner 4y ago
        Rather than speculation it'd be useful if there was more hard science on the subject, you know by actually doing long term experiments on life in space being exposed to these heavy ions. You can find scientific papers on a lot of subjects where it's hard to get at objective fact arguing one way or another and it's hard to tell how factual they really are. Also why would you quote the "upper error bar"? I'd like to know the size of that error bar and what the median is. > The upper error bar right now for a 1000 day Mars mission is upwards of 20% risk of radiation-induced death; most of this is from the heavy ion component of cosmic rays. This is just an argument that you need to bury things in regolith, at least early on, until we get better shielding designed for heavy ions.
  - shortstuffsushi 4y ago
    > in the Hellas basin (where no one particularly wants to land) Why don't people want to land down there? Is it too rough a surface, more so than at higher elevation? Would it be feasible to land outside the basin and make your way down?
    - idlewords 4y ago
      There's a great StackExchange answer on this. Basically, both the terrain and weather are bad: "Sites of areologic interest are far apart, its seasonally induced micro-climate conditions are rough and pronounced due to somewhat larger surface atmospheric pressure, winds are stronger, dust storms longer lasting, it experiences higher seasonal and diurnal surface temperature variations, shorter days and exposure to sunlight during Southern hemisphere winters, and as a deep impact basin, terrain is fairly rugged, inclined, and often covered with deep pockets of sand.” https://space.stackexchange.com/questions/12158/why-has-no-lander-or-rover-visited-hellas-planitia-on-mars https://space.stackexchange.com/questions/12158/why-has-no-l...
    - tsimionescu 4y ago
      The thing is, if you intend to do something like establishing a completely self-sustaining population on Mars (one that could live indefinitely of the earth disappeared), then you need to have a presence in many many places on Mars, because you need access to numerous raw materials. For a simple visitation mission, you can pick an easy place, sure (the other reply points out why this basin is not in fact that easy). But this does nothing to prove that long-term habitation of Mars is in any way possible.

JumpCrisscross 4y ago

> relativistic iron nuclei The Martian atmosphere is 1/166th the density of Earth's [1]. At the ISS's altitude, it's something like a trillionth. [1] https://en.wikipedia.org/wiki/Atmosphere_of_Mars https://en.wikipedia.org/wiki/Atmosphere_of_Mars

idlewords 4y ago
The Martian atmosphere does not provide meaningful shielding against heavy ion radiation unless you're way down in the Hellas basin (where no one particularly wants to land). You reduce the flux by half compared to deep space just by having a big rock blocking half of the sky, but you'll still get all the cancer sooner than later.
- ericbarrett 4y ago
  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?
- mlindner 4y ago
  The Martian atmosphere may not but the surface of the planet does, cutting half the yearly dose versus being in deep space. And I'm not sure I buy the argument that the atmosphere provides little protection. There's a lot of atmosphere there still, enough you can push down on it and rise into the sky if you have some carbon fiber blades moving at very high speeds. I'd think a iron nuclei would hit a lot of atoms on the way down. > you'll still get all the cancer sooner than later. Cancer risk from radiation is probabilistic. If you spend all day outdoors then you increase your lifetime risk of cancer by a significant degree, but it's not like you're definitely going to get cancer. Additionally, most habitation modules, at least early on, are planned to be buried in martian regolith. Also the moon is worse than Mars in all respects with regard to this so you're effectively arguing that humans should never leave the orbit of Earth. I'm not a fan of that future. (BTW, we deal with much higher radiation levels in hot cells in reactors here on Earth, and those even have windows into them. I'm sure we can work out something.)
  - idlewords 4y ago
    You don't have to buy the argument; you can look up the scientific papers. Heavy ion radiation is hard to shield against and creates high energy secondary radiation when it hits air, metal, or rock. Moreover, there is strong evidence cancer risk from heavy ions is considerably greater than predicted by the absorbed dose model we use for other kinds of ionizing radiation. Search on "non targeted effects heavy ions" to read up on this; it's a fascinating topic. The upper error bar right now for a 1000 day Mars mission is upwards of 20% risk of radiation-induced death; most of this is from the heavy ion component of cosmic rays.
    - mlindner 4y ago
      Rather than speculation it'd be useful if there was more hard science on the subject, you know by actually doing long term experiments on life in space being exposed to these heavy ions. You can find scientific papers on a lot of subjects where it's hard to get at objective fact arguing one way or another and it's hard to tell how factual they really are. Also why would you quote the "upper error bar"? I'd like to know the size of that error bar and what the median is. > The upper error bar right now for a 1000 day Mars mission is upwards of 20% risk of radiation-induced death; most of this is from the heavy ion component of cosmic rays. This is just an argument that you need to bury things in regolith, at least early on, until we get better shielding designed for heavy ions.
- shortstuffsushi 4y ago
  > in the Hellas basin (where no one particularly wants to land) Why don't people want to land down there? Is it too rough a surface, more so than at higher elevation? Would it be feasible to land outside the basin and make your way down?
  - idlewords 4y ago
    There's a great StackExchange answer on this. Basically, both the terrain and weather are bad: "Sites of areologic interest are far apart, its seasonally induced micro-climate conditions are rough and pronounced due to somewhat larger surface atmospheric pressure, winds are stronger, dust storms longer lasting, it experiences higher seasonal and diurnal surface temperature variations, shorter days and exposure to sunlight during Southern hemisphere winters, and as a deep impact basin, terrain is fairly rugged, inclined, and often covered with deep pockets of sand.” https://space.stackexchange.com/questions/12158/why-has-no-lander-or-rover-visited-hellas-planitia-on-mars https://space.stackexchange.com/questions/12158/why-has-no-l...
  - tsimionescu 4y ago
    The thing is, if you intend to do something like establishing a completely self-sustaining population on Mars (one that could live indefinitely of the earth disappeared), then you need to have a presence in many many places on Mars, because you need access to numerous raw materials. For a simple visitation mission, you can pick an easy place, sure (the other reply points out why this basin is not in fact that easy). But this does nothing to prove that long-term habitation of Mars is in any way possible.