[burtonator]

There's simply no way that this type of fungus could absorb enough radiation simply because it's not dense enough.

If you want to absorb radiation you have to block it which means it has to come into contact with matter.

The only way you can do this is to have either a smaller volumetric amount of something that's dense (lead, gold, uranium, etc) or a LARGE amount of something less dense (water, concrete, etc).

If you're just talking about an organic organism, sure, it can use the radiation BUT you'd need to have a MASSIVE amount of it in terms of volume and weight.

Simply put, the fungus itself is sparse when looking at it from a subatomic perspective. Most of the radiation passes right through it.

[chongli]

I think the whole framing of this discussion is inappropriate. The interesting thing about this fungus is that it can use the radiation as an energy source to sustain life. The fact that we can’t use the fungus as some kind of miracle lightweight radiation shield is missing the point.

Here we have a life form that has adapted to make use of a very unusual (on earth’s surface, anyway) energy source. That should not be taken for granted. It’s an amazing demonstration of the adaptability of life. It also warrants a deeper investigation into how this ability works and how it came about by evolutionary processes.

[eloff]

Agreed, lead blocks radiation quite well. I don't know why anyone would care about that property in a fungus. What is fascinating is that life evolved a novel energy pathway here, this is like photosynthesis but with gamma radiation. I'd love to know more about it.

[0xdeadb00f]

> I don't know why anyone would care about that property in a fungus.

My thought would be the possibility of it being cheaper to produce than lead, possible to farm it. That could mean a more lightweight material for insulated suits and stuff along those lines.

[TheOtherHobbes]

It's unlikely to be much use for shielding for reasons the top comment explains.

The real reason to care is because it's an interesting - almost textbook - example of evolution operating in a challenging environment.

[0xdeadb00f]

> It's unlikely to be much use for shielding for reasons the top comment explains.

I did read the comment - I know it can't be used for that. I only said that as a more generic response to "I don't know why anyone would care" about this property being found in a fungus - a statement which seemed to lack any imagination imo.

> The real reason to care is because it's an interesting - almost textbook - example of evolution operating in a challenging environment.

This is true! Good point.

[specialist]

"It’s an amazing demonstration of the adaptability of life."

Ya. Just as awesome as chemosynthetic life forms adapted for hydrothermal vents.

It's hard not to be dumb stuck.

[jojobas]

Absorbtion is a misnomer.

It uses a tiny fraction of energy of whatever particle it is. In terms of attenuation it cant be different from anything else of similar density and composition.

[acidburnNSA]

But then why this seemingly-ridiculous line from the article?

> Scientists are thinking of shielding astronauts and space objects with a layer of this radiation-absorbing protective fungus.

[xsmasher]

Because the "article" is a clickbait Youtube video from a channel with videos like "Is the world ending in 2020?" and "Ghost caught on tape in my apartment." It doesn't even name the scientists.

I went searching for "NASA Chernobyl fungus" and found a paper about using it as a shield on mars: https://www.biorxiv.org/content/10.1101/2020.07.16.205534v1

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

It makes more sense in the Mars context, where you might not have lead available, and where growing a large amount of fungus from a small seed packet is a big bonus.

[08-15]

Because NASA is no longer relevant, but desperately wants to be. So they publish anything, and anlways with a sensational headline: microbes that incorporate arsenic into biomolecules, reactionless microwave propulsion, and not fungal radiation shields.

That line doesn't just seem ridiculous, it is.

[DarthGhandi]

Given we are taking about space here I'm quite sure water outperforms per kg compared to the others you've mentioned.

Fairly certain there's no high-Z solid that could compete on cost to orbit.

[raverbashing]

Density blocks radiation but it's the "hard way" of doing it

It's better to have something that resonates in the frequencies you want to block.

Given that melanin already works in the UV range it's not surprising that maybe with some changes it works with higher frequencies (though not too trivial neither because of the way quantum physics work)

[acidburnNSA]

I work in ionizing radiation transport. We use materials with high electron densities to shield gamma rays. Should we be using a material that "resonates" with gamma rays instead? If so could you provide an example of this working on gamma rays?

[ckdarby]

I down voted your comment, here is why.

Working in transporting this material I'd gather you'd have expertise related to this.

Could you better explain why the existing approach is used?Can you counter the arguments made by what you're replying on? Is your comment providing value or information to who you're replying to?

[acidburnNSA]

Thank you for explaining!

Gamma rays interact with atomic electrons and get slowed down via the photoelectric effect, compton scattering, and pair production [1]. Depending on the energy of the gamma ray, different fractions of those interactions will dominate. The ones that matter most for most ionizing gamma rays we encounter work better if there are more electrons packed in. So we use high density materials like lead because they have lots of electrons to stop gamma rays.

No where on this list of tools have I ever seen "materials that resonate with the radiation" so I'm just asking what the heck kind of radiation shielding physical effect is being referred to.

[1] https://fas.org/sgp/othergov/doe/lanl/lib-www/la-pubs/003263...

[raverbashing]

You are right of course, but the effects you're describing are kind of what I meant

Yes, I don't think there is a magic material that will perfectly resonate with high energy gamma rays. But evolution might be able to figure it out. Maybe "resonance" is more specific, and "interaction" is better.

My criticism was more to the " you need thick material to stop radiation" whereas the answer is more "we need thick material because that's the best material we know for the job". Glass is opaque to UV which is more energetic than visible light for example.

And not to forget we know if some materials that do absorb gamma rays, the issue is that they like to go boom after doing that https://en.m.wikipedia.org/wiki/Photofission

[acidburnNSA]

Just quick response on the last point: Photofission reactions happen all the time in places like nuclear reactors. There are no materials that I'm aware of that photofission explosively. The photofission reactions are generally very rare compared to all the other reactions. Heck, natural uranium in your kitchen counter spontaneously fissions all the time but that doesn't lead to an explosion because 1 million atoms is a lot less than 1e23 atoms. Am I missing something?