When the Chernobyl reactor exploded in 1986, it left behind a scar so severe that scientists believed nothing could survive within its core. After the disaster, the shattered reactor complex became a warning.
Nearly four decades later, researchers noticed something that defied every expectation amid cracked concrete and contaminated steel.
A ‘black fungus’ started taking hold quietly inside the most radioactive chambers of the ruined plant. Spreading in patterns across the walls saturated with lethal radiation, the organism was not merely surviving but actively growing and healing itself. This unlikely survivor is now being studied as a potential biological shield for astronauts exposed to radiation in space.
Fungus Is Thriving In Radiation Where Humans Could Not
The 30km exclusion zone surrounding the reactor, often called the “Zone of alienation”, was meant to keep humans away indefinitely. Wildlife outside the reactor complex has started to rebound in the absence of people, but inside the reactor building itself, radiation levels remained extreme.
The black fungus was observed on the ceilings, walls, and inside metal channels, which were meant to protect the electrical cables. The fungus was documented by Ukrainian microbiologist Nelli Zhdanova in 1997, who entered the site. This was not an ordinary fungus infestation; the mould growth was dense, and it showcased shadow-like patterns.
The soil surveys conducted earlier had already shown that fungi in the area appeared to cluster near radioactive particles. And now, the organisms had extended their reach all the way to the radiation’s source.
The “Reactor’s Shadow”
The research compiled by Zhandova identified 37 species of fungus from 19 genera, noting that those richest in melanin were most common in areas of the heaviest infestation, specifically Cladosporium sphaerospermum.
This pigment, which is commonly found in humans, gave the fungus its distinct dark colouration, and it quickly became central to understanding how the organism might be interacting with radiation. This colour gave this fungus a haunting nickname called “the reactor’s shadow.”
Melanin had long been known to protect living cells from ultraviolet radiation. In humans, darker skin absorbs and dissipates harmful UV rays more effectively. But what Zhandova was witnessing suggested that these fungi were not just shielding themselves from radiation, but they appeared to be responding to it.
She coined the term “radiotropism” to describe what she observed. The fungal growth is oriented toward ionising radiation, which is vastly more energetic than visible light, capable of shredding DNA, destroying proteins, and killing cells.
According to the research conducted by Zhandova and Ekaterina Dadachova, a nuclear scientist at the Albert Einstein College of Medicine in New York in 2007, they carried out numerous experiments on melanised fungi that were exposed to radiation.
According to the research, ionising radiation carries roughly one million times more energy than visible light. Dadachova theorised that melanin could act as a biological energy transducer, absorbing radiation and converting it into a form usable by cellular processes. While the fungi do not neutralise radioactive isotopes or “eat” radiation in a literal sense, they may harness its energy to fuel growth.
Limits and Scientific Debate Over Radiotropism
When it comes to research and documents, not all scientists are convinced. Follow-up studies revealed that not every fungus exhibits radiotropism. A 2006 survey by Zhdanova found that only nine of 47 melanised species consistently grew toward radioactive sources. In 2022, researchers at Sandia National Laboratories observed no growth advantage in certain fungi exposed to radiation. These findings suggested that the phenomenon is species-specific, not universal.
Why NASA Is Eyeing This Fungus
Samples of the fungus growing in the Chernobyl explosion unit were sent to the International Space Station (ISS) as part of an experiment designed to test both growth behaviour and radiation-shielding potential. Unlike Chernobyl, space presents a radiation environment.
Beyond Earth’s atmosphere and magnetic field, astronauts are bombarded by galactic cosmic radiation, high-energy particles originating from exploding stars across the universe.
These particles travel near the speed of light and can penetrate spacecraft walls and even human tissue. NASA has described cosmic radiation as one of the greatest hazards to long-duration spaceflight. After 26 days aboard the ISS, the results were striking.
Compared to control samples on Earth, the fungi exposed to space radiation grew 1.21 times faster. Researchers caution that microgravity may have contributed to the growth increase. Ongoing experiments aim to separate the effects of radiation from zero gravity. Still, the second part of the experiment delivered a more concrete result.
A radiation sensor placed beneath a thin layer of the fungus recorded a measurable reduction in radiation exposure. As the fungal layer thickened, its shielding effect increased. Even a smear of melanin-rich biomass reduced radiation levels across the measured spectrum.
NASA’s “Passive Radiation Shielding” Approach For Space Missions
Traditional radiation shielding relies on dense materials, and these materials are costly, heavy, and difficult to transport. According to the Indian Defence Review, “Producing materials in space is expensive—about $1,000 to send just a can of soda into low Earth orbit. Growing fungi in orbit, rather than transporting materials from Earth, could significantly reduce costs.”
Unlike metal shielding, fungal shielding could be grown in space, repairing itself, adapting to damage and increasing in thickness over time. NASA researchers describe this approach as “Passive Radiation Shielding” using layered, multifunctional materials rather than brute mass. A living shield could line the spacecraft walls, habitats, or storage modules, reducing radiation exposure continuously.
Advantage Of The Fungus
The fungus offers advantages that no traditional material can match. Studies show it can repair its own DNA, even after radiation damage. It actively grows toward radiation sources, forms dense protective layers, and thrives in environments lethal to most organisms.
Its melanin absorbs radiation not by deflecting it, but by dissipating its energy, reducing secondary damage caused by reactive ions. This antioxidant property further limits harm to surrounding biological tissue. The fungus is not literally ‘eating’ the radiation, but adapting to it.
Fungus Is More Than A Shield
Researchers, including Aaron Berliner of Weill Cornell Medicine and Nils Averesch of the University of Florida, are exploring additional applications. The fungus can consume dead organic matter and potentially break down plastics and human waste, turning refuse into usable biomass.
For astronauts travelling months or years away from Earth, reducing reliance on resupply missions is critical. A fungus that grows, protects, and recycles could become part of a broader biological infrastructure for space habitation.
From Nuclear Ruins To Deep Space
The idea that a mould growing from one of the deadliest disasters might help protect astronauts on space missions is striking. Chernobyl was once seen as a place where life ended. Instead, it became a laboratory revealing how life adapts under extreme pressure.
While radiosynthesis remains under investigation, the fungus does not make space safe, but it may make it safer. As Berliner has noted, the story is not just about science. It is about survival.
