Some things grow in darkness. Others feed on it.
Deep in the irradiated skeleton of Reactor 4, Chernobyl’s sarcophagus of steel and concrete, scientists discovered something that should not exist: life. Not just surviving, but thriving. A black fungus clinging to the charred graphite of a nuclear core, growing toward the radiation like moss stretching toward sunlight.
The name? Cladosporium sphaerospermum. A harmless-sounding organism with a truly alien appetite.
What this fungus does is more than resist radiation, it consumes it, transforming invisible death into metabolic energy through a process scientists now call radiosynthesis.
And it’s not just a freak of Chernobyl. It’s already been tested in space. It may one day shield astronauts from cosmic death rays on Mars. And it might hold the key to cleaning up nuclear hellscapes back here on Earth.
But let’s start at ground zero.
Born in the Fallout
When researchers from the Ukrainian National Academy of Sciences first surveyed the interior of the Chernobyl reactor decades after the explosion, they found something bizarre: black moulds had colonised nearly every irradiated surface. Around 80% of the fungi were melanised, dark-hued species rich in the pigment melanin, which usually protects against UV rays or pathogens.
But in this case, melanin was doing something far stranger. The fungi weren’t just enduring the radiation, they were growing toward it.
This behaviour was termed radiotropism, akin to the way plants grow toward light. The fungi extended their hyphae directly into the most radioactive graphite debris they could find, as if hunting energy itself.
This led to a bigger question: what if they were?
Not Just Surviving, Feeding
The leading suspect behind this bizarre metabolism is melanin, a ubiquitous biological pigment found in skin, hair, squid ink… and black moulds. In radiotrophic fungi, melanin doesn’t just block radiation, it appears to harvest it.
Expose melanin to ionising radiation, and its electronic structure shifts, amplifying its electron spin resonance signal fourfold. That’s not just absorption, that’s activation.
These shifts likely enhance the fungi’s metabolic pathways, boosting their TCA cycle intermediates and accelerating growth, confirmed in lab tests that show melanised fungi grow faster when bombarded with gamma radiation than in normal conditions.
Even in low Earth orbit, where space radiation bombards living cells from every direction, Cladosporium sphaerospermum didn’t just survive. It grew 21% faster than its Earth-bound controls.
Which means one thing: this fungus doesn’t just tolerate space, it wants to be there.
Beyond Earth: A Living Shield
NASA and other agencies have quietly taken notice.
The most critical challenge in space colonisation isn’t propulsion, AI, or even food, it’s radiation. A single Mars mission would expose astronauts to levels of cosmic radiation capable of frying DNA like bacon in a microwave.
Current solutions, lead, water, regolith, are either too heavy or too logistically insane. But a fungus that grows into a radiation shield? That changes the equation entirely.
A 21cm-thick wall of C. sphaerospermum could theoretically block 100% of the radiation you’d get on the Martian surface. Combine that with local Martian soil, and you can cut that to just 9cm.
And it’s self-replicating.
Bring a few grams. Feed it. It grows. It shields. It even heals itself if damaged by radiation, because the radiation is its food.
What NASA is testing isn’t a material. It’s a biological infrastructure strategy.
A Nuclear Cleanup Crew
Meanwhile, back on Earth, the same traits that make this fungus a candidate for Mars make it a dream tool for radioactive waste management.
These fungi don’t just survive in contaminated zones, they actively sequester radioactive isotopes inside their cellular walls. Some even engulf hot particles, binding to the most toxic graphite and plutonium remnants left in the Chernobyl core.
Forget bulldozers and lead coffins. Imagine a bioreactor powered by radioactive waste itself, with fungi growing around and entombing nuclear particles in a living sarcophagus.
It’s slow. But it works. And it’s sustainable.
There’s Just One Catch
Like all great horror stories, there’s a sting in the tail.
Cladosporium is one of the most common airborne moulds in the world. And while it rarely causes serious harm, it’s a known allergen and an opportunistic pathogen, especially for the immunocompromised.
A 9cm fungal wall wrapped around a Martian base sounds clever, until it starts pumping spores into your life support system. The same shielding that protects you could slowly clog your lungs.
Any future use of radiotrophic fungi in closed environments, spacecraft, moon bases, nuclear cleanup sites, will require obsessive containment, filtration, and monitoring. You can’t just put a leash on something that thrives where everything else dies.
Final Transmission
A fungus that eats radiation isn’t science fiction anymore. It’s biology adapting to the unthinkable. And it’s already been to space.
Whether it becomes the foundation of our off-world habitats or the biological broom sweeping up our radioactive past, one thing is clear: this is no ordinary mould.
This is evolution finding a way to live off death.
And it’s just getting started.