Quote of the Day

The explosion of the No. 4 reactor of the Chernobyl Nuclear Power Plant near Pripyat, Ukraine on April 26, 1986 remains the worst nuclear disaster in human history. It left a 30-kilometer exclusion zone—a deserted landscape where high radiation levels remain even now, decades after the incident—where human settlement and habitation are restricted.

Within this zone, however, scientists have discovered an unlikely survivor: a resilient black fungus called Cladosporium sphaerospermum. After the Chernobyl disaster, scientists observed patches of blackened growths on the walls of the No. 4 reactor—fungi that seemed to thrive where the radiation was highest.

This fungus has adapted to a level of radiation that would be lethal for most life forms. Even more fascinating is its ability to “feed” on this radiation, using it as a source of energy, similar to how plants use sunlight for photosynthesis.

Further research discovered that C. sphaerospermum and some other black fungi species, like Wangiella dermatitis and Cryptococcus neoformans, possessed melanin, the pigment responsible for human skin color. However, in these fungi, the melanin served a different purpose: it absorbed radiation, which was then converted into usable energy, allowing it to grow in areas with intense radioactive exposure.

Scott Travers
November 2, 2024
This Black Fungus Might Be Healing Chernobyl By Drinking Radiation—A Biologist Explains

About 20 years ago I read Rare Earth: Why Complex Life is Uncommon in the Universe about the possibility of intelligent life elsewhere in the universe. It went through all the requirements for life and the relative odds of all those things happening simultaneously such that intelligent life had time to evolve. It concluded it was very unlikely. The requirements were varied. The planet would require millions of years without being pulverized by one or more collisions with other large rocks. The atmosphere needed to be oxygen rich and relatively stable for hundreds of thousands of years or millions of years. The planet needed a magnetic field to protect the surface from radiation. The planet itself could not be radioactive. The gravity had to be great enough to retain an atmosphere but not so great that it would crush biological lifeforms. The type of star needed to be something stable and of the correct color for millions of years. Etc., etc.

I was annoyed with the authors for several reasons. But the biggest reason was the low radiation requirement. The author was quite certain that high, by our standards, radiation levels were deadly to life. But my response to this claim was, “Why couldn’t there exist lifeforms which required radiation to thrive?”

This fungus demonstrates life does not require the low radiation levels the authors claimed by the authors. Agreed, fungus is not intelligent life. But given a million years or so…

I asked Copilot to help me find the name of the book and a follow-up question:

Joe: I had a disagreement with the authors because I suspected it was possible that life could evolve to even require radiation for survival. I recently read about radiotrophic fungi. This supports my hypothsis. Do you have any further thoughts on this line of thinking?

Copilot: Your idea is intriguing—and definitely pushes us to expand what we consider “habitable.” The classic perspective, as laid out in Rare Earth, emphasizes that complex life needs an environment free from excessive radiation. However, when we see examples like radiotrophic fungi, nature challenges that view.

These fungi, most notably observed around Chernobyl and in other extreme settings, seem to not only tolerate but perhaps even harness ionizing radiation. Researchers have noted that species such as Cryptococcus neoformans and Cladosporium sphaerospermum increase in biomass when exposed to high-radiation conditions. The hypothesis is that melanin—the pigment that gives these fungi their dark color—plays a role similar to chlorophyll in photosynthesis by capturing energy from radiation. This process, sometimes described as “radiosynthesis,” suggests that under the right conditions, radiation might actually drive metabolism rather than simply causing damage.

From an evolutionary standpoint, this raises the possibility that radiation might not always be purely destructive. In niches where traditional energy sources (like sunlight or chemical feedstocks) are scarce, harnessing radiation could theoretically be an alternative pathway to energy. Of course, such adaptations come with a cost. The same ionizing radiation that could provide energy also increases mutation rates and cellular damage, so any organism evolving along this path would need robust repair mechanisms. For example, bacteria like Deinococcus radiodurans already offer evidence of extreme radiation resistance through efficient DNA-repair processes. In essence, these adaptations expand our conception of what conditions might support life, especially in environments that we previously dismissed as too hostile.

The implications for astrobiology are fascinating. If life on Earth can evolve to co-opt radiation, then perhaps other planets or moons bathed in high radiation—whether from a weak magnetic field, proximity to certain stars, or other cosmic events—could host organisms that have turned radiation from a hazard into a resource. This challenges the “Rare Earth” idea by offering a counterargument: while many environments might be inhospitable to common forms of life, evolution might take unexpected turns that allow life to adapt in ways we haven’t traditionally envisioned.

Your hypothesis invites a broader discussion on the adaptability of life. It encourages us to rethink habitability by not strictly equating high radiation with uninhabitability. Instead, we might need to explore a spectrum of environmental niches where life might not just endure, but require—and even utilize—what we once thought was universally harmful radiation. This opens many avenues for further exploration: What mechanisms would support such life forms? How might their biochemistry differ from terrestrial norms? And could these principles eventually inform our search for extraterrestrial life or even novel biotechnologies?

Interesting thoughts.