Mould from Chernobyl nuclear reactor tested as radiation shield on ISS

[blasphemer]

https://www.biorxiv.org/content/10.1101/2020.07.16.205534v1

https://futurism.com/the-byte/fungus-chernobyl-protect-astronauts-cosmic-rays

https://www.newscientist.com/article/2249784-mould-from-chernobyl-nuclear-reactor-tested-as-radiation-shield-on-iss/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=news

At full maturity, radiation beneath a ≈ 1.7 mm thick lawn of the melanized radiotrophic fungus (180° protection radius) was 2.17±0.35% lower as compared to the negative control. Estimations based on linear attenuation coefficients indicated that a ~ 21 cm thick layer of this fungus could largely negate the annual dose-equivalent of the radiation environment on the surface of Mars

Thoughts?

[Pete]

It's about as good a shield per thickness as paper.
a bit better than water or aluminum.

Potentially self-repairing, but intrinsically more fragile than any solid material.

[DistantTemple]

Negative: could complicate planetary protection.
Positive: If it can live in the open on Mars it could be the start of a designed Mars ecology. I assume it cannot live in the open... but greening Mars is not just straight to trees and grass pastures... Fungi, micro organisms.... cacti....

[1]

At full maturity, radiation beneath a ≈ 1.7 mm thick lawn of the melanized radiotrophic fungus (180° protection radius) was 2.17±0.35% lower as compared to the negative control. Estimations based on linear attenuation coefficients indicated that a ~ 21 cm thick layer of this fungus could largely negate the annual dose-equivalent of the radiation environment on the surface of Mars

Thoughts?

Unfortunately, the rest of that cropped sentence says all that really needs to be said.

whereas  only ~ 9 cm  would  be  required with  an  equimolar  mixture  of  melanin  and  Martian  regolith.

Or, even more easily, just use regolith by itself. The easiest way to "reduce upmass" is to use mass that already exists at your landing site.

So the better question is, can this fungus do something else that can be useful on site? For example, a possible use for fungus on Mars could be for extraction of otherwise trace amounts of heavy metals; especially in the very early phases of colonization when standard industrial methods just aren't an option. In that way, the radiation tolerance of this fungus, while not all that useful for shielding, might still be quite useful in that this fungus might be easier to cultivate in an environment that would kill most other organisms.

IMO, this is in the 'interesting, but not immediately useful' category. 

[Robotbeat]

Yeah, I don't see the point of this fungus versus just some polyethylene or water or whatever.

[john smith 19]

whereas  only ~ 9 cm  would  be  required with  an  equimolar  mixture  of  melanin  and  Martian  regolith.

Or, even more easily, just use regolith by itself. The easiest way to "reduce upmass" is to use mass that already exists at your landing site.

IIR the usual figure of martian regolith necessary to give equal protection as the full depth of the earths atmosphere is 3m.

So either is quite an improvement. Either is (in principle) low maintenance. Key question with the inorganic option (regolith + melanin) would be does the melanin break down over time? If it now needs to be monitored and either refreshed or replaced.

[1]

IIR the usual figure of martian regolith necessary to give equal protection as the full depth of the earths atmosphere is 3m.

Yes, and there's good reason for that. On the top of page 6 of the paper, bold mine:

Only valid for photonic radiation (from 1 keV to 20 MeV)²⁶, calculations based on LACs were based on the assumption that no alpha- and beta- particles could reach the experiment, as neither will be able to penetrate the hull of the ISS³³. Other high-energy (HZE) ions were not respected either, and the analysis focused on ionizing electromagnetic radiation, within the absorption spectrum of the employed Geiger counters (cf. supplementary file 1, section B).

Now, this is actually very reasonable for an experiment run on the ISS. They're correct about the existing shielding on ISS blocking low energy particles, and the Earth does a pretty good job of shielding things in ISS's orbit from solar protons and some not-so-high energy ions. The problem is extrapolating the effectiveness of photonic-only attenuation towards calculating the effectiveness of reducing a cumulative total dose on the surface of Mars.

Oversimplifying a bit here, but stopping photons, even gamma rays, is comparitively easy. What we really need from that 3m of regolith is stopping power for cosmic rays, solar protons, and all of the resulting secondary particles that result when they smash into the martian surface. So the most likely resolution to the size discrepancy is that all of the estimates presented in that paper are actually far too small; and that one could easily need 5-10m of fungus to provide the same cumulative total dose protection as 3m of pure regolith.

[Pete]

From they numbers, it seems that they defined "could largely negate the annual dose-equivalent of the radiation environment on the surface of Mars" as "stops 95% of gamma"

[libra]

My mind is blown. What is sure is: whatever thrieved inside Chernobyl radiation hotbed, should find space radiation pretty harmless... kind of walk in the park for the hardboiled fungi (fungus ?)

[blasphemer]

Oversimplifying a bit here, but stopping photons, even gamma rays, is comparitively easy. What we really need from that 3m of regolith is stopping power for cosmic rays, solar protons, and all of the resulting secondary particles that result when they smash into the martian surface. So the most likely resolution to the size discrepancy is that all of the estimates presented in that paper are actually far too small; and that one could easily need 5-10m of fungus to provide the same cumulative total dose protection as 3m of pure regolith.

This. Thanks for the explanation. So nothing revolutionary here and you still need several meters of shielding to stop GCRs.

[Robotbeat]

Yeah. Nuclei traveling at near the speed of light don’t care if they’re hitting alive or dead material, they just care about what atoms they’re hitting: how many atoms and how many protons and neutrons they have.

[Twark_Main]

Yeah. Nuclei traveling at near the speed of light don’t care if they’re hitting alive or dead material, they just care about what atoms they’re hitting: how many atoms and how many protons and neutrons they have.

Yep. And they don't care whether the resultant energy gets converted to chemical potential energy ("eaten"), or simply turned into heat.

I seriously doubt that it would represent a non-trivial source of energy, especially considering the work required to harvest it.

[Robotbeat]

Yeah. Nuclei traveling at near the speed of light don’t care if they’re hitting alive or dead material, they just care about what atoms they’re hitting: how many atoms and how many protons and neutrons they have.

Yep. And they don't care whether the resultant energy gets converted to chemical potential energy ("eaten"), or simply turned into heat.

I seriously doubt that it would represent a non-trivial source of energy, especially considering the work required to harvest it.

Absolutely trivial.

Mars has about 10-20 rem/year of cosmic radiation (and it is mostly cosmic rays), which is the same as 100-200mSv/year or 0.1-0.2 Seivert/year. Now, to convert from Seivert (biological effect of radiation) to Gray (Joules per kilogram of radiation), you need the “quality factor.” By definition, this is “1” for gamma rays. For Mars surface radiation, you’re talking probably about 20 quality factor since it’s mostly cosmic rays that cause the biological effect there. So 0.005-0.01 J/kg/year of radiation. For a density of water and a 20cm thickness, that’s 200kg/m^2, and so about 1-2Joules/m^2/year, let’s say an average of 1.5J/m^2/year. There are about 30,000,000 seconds in a year, so about 5*10^-8 Watts/m^2, 50nanowatts/m^2.

But let’s just give the benefit of the doubt and say that’s all gamma rays. 0.1-0.2 Joules/kg or 10^-5 W/m^2. 10 microwatts/m^2.

Sunlight on Mars is about 600W/m^2 during the day. Let’s call it an average of 100-200W/m^2.

So this energy source is at least 7-8 orders of magnitude smaller than sunlight on mars.

[Twark_Main]

Yeah. Nuclei traveling at near the speed of light don’t care if they’re hitting alive or dead material, they just care about what atoms they’re hitting: how many atoms and how many protons and neutrons they have.

Yep. And they don't care whether the resultant energy gets converted to chemical potential energy ("eaten"), or simply turned into heat.

I seriously doubt that it would represent a non-trivial source of energy, especially considering the work required to harvest it.

Absolutely trivial.

Mars has about 10-20 rem/year of cosmic radiation (and it is mostly cosmic rays), which is the same as 100-200mSv/year or 0.1-0.2 Seivert/year. Now, to convert from Seivert (biological effect of radiation) to Gray (Joules per kilogram of radiation), you need the “quality factor.” By definition, this is “1” for gamma rays. For Mars surface radiation, you’re talking probably about 20 quality factor since it’s mostly cosmic rays that cause the biological effect there. So 0.005-0.01 J/kg/year of radiation. For a density of water and a 20cm thickness, that’s 200kg/m^2, and so about 1-2Joules/m^2/year, let’s say an average of 1.5J/m^2/year. There are about 30,000,000 seconds in a year, so about 5*10^-8 Watts/m^2, 50nanowatts/m^2.

But let’s just give the benefit of the doubt and say that’s all gamma rays. 0.1-0.2 Joules/kg or 10^-5 W/m^2. 10 microwatts/m^2.

Sunlight on Mars is about 600W/m^2 during the day. Let’s call it an average of 100-200W/m^2.

So this energy source is at least 7-8 orders of magnitude smaller than sunlight on mars.

Yep, that's what I thought. Thanks for doing the math! It's amazing how tiny the energy production potential really is.

[Robotbeat]

Yeah. Nuclei traveling at near the speed of light don’t care if they’re hitting alive or dead material, they just care about what atoms they’re hitting: how many atoms and how many protons and neutrons they have.

Yep. And they don't care whether the resultant energy gets converted to chemical potential energy ("eaten"), or simply turned into heat.

I seriously doubt that it would represent a non-trivial source of energy, especially considering the work required to harvest it.

Absolutely trivial.

Mars has about 10-20 rem/year of cosmic radiation (and it is mostly cosmic rays), which is the same as 100-200mSv/year or 0.1-0.2 Seivert/year. Now, to convert from Seivert (biological effect of radiation) to Gray (Joules per kilogram of radiation), you need the “quality factor.” By definition, this is “1” for gamma rays. For Mars surface radiation, you’re talking probably about 20 quality factor since it’s mostly cosmic rays that cause the biological effect there. So 0.005-0.01 J/kg/year of radiation. For a density of water and a 20cm thickness, that’s 200kg/m^2, and so about 1-2Joules/m^2/year, let’s say an average of 1.5J/m^2/year. There are about 30,000,000 seconds in a year, so about 5*10^-8 Watts/m^2, 50nanowatts/m^2.

But let’s just give the benefit of the doubt and say that’s all gamma rays. 0.1-0.2 Joules/kg or 10^-5 W/m^2. 10 microwatts/m^2.

Sunlight on Mars is about 600W/m^2 during the day. Let’s call it an average of 100-200W/m^2.

So this energy source is at least 7-8 orders of magnitude smaller than sunlight on mars.

Yep, that's what I thought. Thanks for doing the math! It's amazing how tiny the energy production potential really is.

Yep, I always think about that whenever anyone suggests "harnessing radiation" or saying that radiation will degrade plastics on Mars or whatever... UV might (it's orders of magnitude stronger than this), but overall, there's just so little energy involved, that unless you have some weird metastable chemical, you just don't have to worry about cosmic ray or solar energy particle radiation effects on the surface of Mars...