[ExI] Chernobyl fungus could shield astronauts from cosmic radiation

[sparge]

https://bigthink.com/surprising-science/radiation-on-mars-fungus?rebelltitem=1#rebelltitem1

A recent study tested how well the fungi species Cladosporium
sphaerospermum blocked cosmic radiation aboard the International Space
Station.

   - Radiation is one of the biggest threats to astronauts' safety during
   long-term missions.
   - C. sphaerospermum is known to thrive in high-radiation environments
   through a process called radiosynthesis.
   - The results of the study suggest that a thin layer of the fungus could
   serve as an effective shield against cosmic radiation for astronauts.
   - When astronauts return to the moon or travel to Mars, how will they
   shield themselves against high levels of cosmic radiation? A recent
   experiment aboard the International Space Station suggests a surprising
   solution: a radiation-eating fungus, which could be used as a
   self-replicating shield against gamma radiation in space.

The fungus is called Cladosporium sphaerospermum, an extremophile species
that thrives in high-radiation areas like the Chernobyl Nuclear Power
Plant. For C. sphaerospermum, radiation isn't a threat — it's food. That's
because the fungus is able to convert gamma radiation into chemical energy
through a process called radiosynthesis. (Think of it like photosynthesis,
but swap out sunlight for radiation.)

The radiotrophic fungus performs radiosynthesis by using melanin — the same
pigment that gives color to our skin, hair and eyes — to convert X- and
gamma rays into chemical energy. Scientists don't fully understand this
process yet. But the study notes that it's "believed that large amounts of
melanin in the cell walls of these fungi mediate electron-transfer and thus
allow for a net energy gain."

Additionally, the fungus is self-replicating, meaning astronauts would
potentially be able to "grow" new radiation shielding on deep-space
missions, instead of having to rely on a costly and complicated
interplanetary supply chain.

Still, the researchers weren't sure whether C. sphaerospermum would survive
on the space station. Nils J.H. Averesch, a co-author of the study
published on the preprint server bioRxiv, told SYFY WIRE:

"While on Earth, most sources of radiation are gamma- and/or X-rays;
radiation in space and on Mars (also known as GCR or galactic cosmic
radiation) is of a completely different kind and involves highly energetic
particles, mostly protons. This radiation is even more destructive than X-
and gamma-rays, so not even survival of the fungus on the ISS was a given."

To test the "radio-resistance" of C. sphaerospermum in space, petri dishes
containing a .06-inch layer of the fungus were exposed to cosmic radiation
aboard the ISS. Dishes containing no fungus were exposed, too. The results
showed that the fungus cut radiation levels by about 2 percent.

Extrapolating these results, the researchers estimated that a roughly
8-inch layer of C. sphaerospermum "could largely negate the annual
dose-equivalent of the radiation environment on the surface of Mars." That
would be a significant benefit to astronauts. After all, an astronaut who
is one year into a Mars mission would have been exposed to roughly 66 times
more radiation than the average person on Earth.

To be sure, the researchers said more research is needed, and that C.
sphaerospermum would likely be used in combination with other
radiation-shielding technology aboard spacecraft. But the findings
highlight how relatively simple biotechnologies may offer outsized benefits
on upcoming space missions.

"Often nature has already developed blindly obvious yet surprisingly
effective solutions to engineering and design problems faced as humankind
evolves – C. sphaerospermum and melanin could thus prove to be invaluable
in providing adequate protection of explorers on future missions to the
Moon, Mars and beyond," the researchers wrote.
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