I feel like I'm taking crazy pills every time I read about this fungus. Let us grant the premise of a fungus somehow harnessing ionizing radiation using melanin; such a fungus could in principle be used to shield radioactive sources, but it won't "eat it up"; the radioactive isotopes emitting that radiation won't be disposed of in any way by the fungus. They don't eat those, and even if they did it wouldn't get rid of them, only incorporate them. Neither chemical nor any kind of biological process can make radioactive isotopes stop being radioactive, you need some sort of nuclear process to do that. The absolute best the fungus could do is bind up the radioactive isotopes to aid in their collection, but epoxy resins sprayed over the contaminated areas are far more effective than that could ever be.

Also, making spacecraft shielding and even furniture out of this stuff? It's the stupidest thing I ever heard. The mass of the fungus doesn't come from ionizing radiation anymore than the mass of a plant comes from sunlight. You might as well claim that you're going to grow trees in space using the abundant sunlight. They power themselves with light but still need to be made out of something! Are they also hoping these fungus like to eat lunar regolith? It makes zero sense, but here we've got the BBC and apparently NASA taking the idea seriously. Where is the fucking biomass meant to come from?? I must be crazy, or they all are.

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storus 28 minutes ago | parent | next [-]

Melanin is used as a solar panel, capturing gamma rays and then passing the resulting consistent flow of excited electrons over to the Krebs cycle with the help of CO2; like in photosynthesis. Humans run on electrons resulting from Krebs cycle as well, just the input is different. By using it as shielding, you'd simply decrease the amount of ionizing radiation hitting humans inside the spaceship. In other words, it would be better than some static material as it consumes part of incoming radiation for its own existence.

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wongarsu 2 hours ago | parent | prev | next [-]

In regards of NASA taking it seriously, my null hypothesis would be that reporters misunderstand NASA just as much as everything else about fungi.

If I understand the linked NASA press releases correctly, they are talking about using a mix of regolith, cyanobacteria and fungi as part of the outer shell of a habitat. The mycelian network of the fungi binds the loose regolith together, forming a strong and somewhat flexible material, with the fungus working a bit like the cement in a concrete mix. And because fungi don't form from nothing you add cyanobacteria that create "fungus food" (presumably some sugar) from water and CO2 (I'm sure you need to add a bit more than that, but that might be beyond the scope of a press release)

This really has nothing to do with radiation-absorbing fungi at all, except for one remark how the melanin in radiation-eating fungi could provide further shielding.

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VladVladikoff 3 hours ago | parent | prev | next [-]

>the radioactive isotopes emitting that radiation won't be disposed of in any way by the fungus. They don't eat those, and even if they did it wouldn't get rid of them

Please excuse the novice question but I am confused, where does the energy come from then?

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mikkupikku 2 hours ago | parent | next [-]

Granting the premise, the fungus gets energy (but not mass) from the natural decay of radioactive particles. It doesn't accelerate that decay, the decay happens at the same pace it would have without the fungus. Just like planting more plants doesn't make the sun burn out any faster. The fungus itself is made of carbon and all the other usual stuff life is made from.

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dr_dshiv an hour ago | parent [-]

What if the fungus accumulated radioactive particles in vesicles? Might they create chained reactions and thus deplete the radioactivity faster than spatially separated particles? Might that be plausible?

	▲	georgefrowny 27 minutes ago \| parent \| next [-]
		Theoretically yes, as long as the isotopes are themselves fissile and susceptible to chain reactions. E.g. U-235 is (obviously, since it's fission reactor fuel) but, say, Iodine-131 undergoes beta decay. That electron can't get into another I-131 atom and cause another decay there like neutrons do in U-325. So piling up I-131 won't get it going faster. In principle if fungi could somehow concentrate enough fissionable material (say uranium), you could get something like the Oklo reactor going, but it would have to be a truly gigantic, probably unphysical amount of fungi to have access to that much environmental uranium in the first place and it would then have to be concentrated very strongly to get any measurable effect. You won't see anything at all if you just move a few atoms a few mm, so it would need to have very long range hyphae. You also need it to be basically one huge organism in order to collect the uranium to one place - billions of small fungi just doing a few square inches each won't work. It's unlikely the fungus could survive to become so huge on only the promise of fractionally higher future radiation, so it would need to eat something else too. And then it would decay into daughter isotopes that don't further benefit from the concentration so it might not help a lot anyway if you're looking for cleanup. Plus you've covered your cleanup site in, presumably, millions of tonnes of fungus which might or might not be an improvement.
	▲	kadoban 44 minutes ago \| parent \| prev \| next [-]
		> Might that be plausible? Not really. You're talking about a fungus creating essentially a nuclear reactor inside of its cells, and creating it out of fuel that's not good enough to make a nuclear reactor in the first place (it at one time was, but now it's a mess of decay products and nonsense). Reactors also take a certain amount of mass. You can't just squish two tiny microgram particles together and hope to get anything going.
	▲	tgv an hour ago \| parent \| prev [-]
		A chain reaction requires several kilograms, densely packed, if I'm not mistaken (https://en.wikipedia.org/wiki/Critical_mass#Bare_sphere). So that's already a tall order for a fungus. But the radio-active material stays in place. These fungi absorb the radiation.

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2 hours ago | parent | prev [-]

[deleted]

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tonyarkles an hour ago | parent | prev | next [-]

I mean... you're completely right and some of the stuff is as ridiculous as you're suggesting (e.g. the furniture). However... what we're agreeing on is that the fungus is absorbing alpha/beta particles and gamma rays that are coming off the radioactive material, which in theory should mean that it would act as a radiation shield. Whether it's a more effective radiation shield than other options is the big question, and for space travel in particular the question I'd want to know is how effective is a given mass of this fungus relative to other options (e.g. water).

	▲	Xss3 39 minutes ago \| parent [-]
		Id like to know about its failure modes. Does the fungus die when kept in less than ideal conditions? How quickly?

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lazide 3 hours ago | parent | prev [-]

Something the fungus COULD do (in a hypothetical world) is concentrate radioisotopes along with some moderator to accelerate the fission process and harvest more energy.

Would probably require a lot more time than it would have, however, considering the relatively low amounts of radioisotopes in todays world (due to the halflife of most of them, and the age of our planet).

Several billion years ago it could have been a thing though!

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Cthulhu_ an hour ago | parent | next [-]

But if it concentrates isotopes to accellerate fission, wouldn't that cause the material to heat up and, ultimately, kill the fungus? Depends on rate of concentration of course, if it just grabs the odd airborne isotope (if that's a thing) then maybe.

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mikkupikku 3 hours ago | parent | prev [-]

Maybe in principle, but neutron radiation from fallout/etc is relatively minimal and you really just have to wait out the decay of those isotopes.

The good news is radiation detectors are insanely sensitive so you can map where the hotspots are and mitigate much of the risk using exclusion zones and / or various cleanup techniques to collect the radioactive material so it can be safety stored.

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lazide 2 hours ago | parent [-]

I think we’re agreeing?

	▲	mikkupikku 2 hours ago \| parent [-]
		Yes