Comment by mikkupikku
4 hours ago
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.
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.
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.
>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?
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.
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?
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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).
Id like to know about its failure modes. Does the fungus die when kept in less than ideal conditions? How quickly?
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!
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.
All living organisms have this problem - people who can’t sweat/are in environments with no effective evaporation die, piles of leaves with fungus can heat up so much they catch on fire and burn, etc.
Most life has evolved some sort of mechanism to control it, but sometimes it doesn’t work right.
If such a fungus existed and we had enough radioactive material lying around for it to survive, I’d expect the occasional random meltdown to occur.
Notably, this happened due to pure natural causes anyway a couple billion years ago! [https://www.iaea.org/newscenter/news/meet-oklo-the-earths-tw...]
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.
I think we’re agreeing?
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