In 1991, scientists discovered a strange form of fungi growing at the Chernobyl Nuclear Power Plant. The organisms seem to feed on radiation, converting gamma rays into energy for growth. Now, researchers from the University of North Carolina at Charlotte and Stanford University are exploring whether these "radiotrophic fungi" could protect astronauts living on the Moon or Mars. A big benefit is that the fungus self-replicate so the material could be grown upon arrival rather than having to be carried into space from Earth. Experiments conducted on the International Space Station suggest that growing a layer of fungus on top of Mars rock could result in a sufficient shield for people stationed on the Red Planet. From their technical paper in bioRxiv:
In search of innovative radiation-shields, biotechnology holds unique advantages such as suitability for in-situ resource utilization (ISRU), self-regeneration, and adaptability. Certain fungi thrive in high-radiation environments on Earth, such as the contamination radius of the Chernobyl Nuclear Power Plant. Analogous to photosynthesis, these organisms appear to perform radiosynthesis, using pigments known as melanin to convert gamma-radiation into chemical energy. It is hypothesized that these organisms can be employed as a radiation shield to protect other lifeforms.[…]
Estimations based on linear attenuation coefficients indicated that a ~ 21 cm thick layer of this fungus could largely negate the annual dose-equivalent of the radiation environment on the surface of Mars, whereas only ~ 9 cm would be required with an equimolar mixture of melanin and Martian regolith. Compatible with ISRU (in-situ resource utilization), such composites are promising as a means to increase radiation shielding while reducing overall up-mass, as is compulsory for future Mars-missions.
image: "Cryptococcus neoformans stained with light India ink," CDCP (public domain)