I've often noted that fungi are the forgotten heroes of the ecosystem, beavering away largely out of sight and therefore out of mind. Whether it's the ability to break down plastic waste or their use as meat substitutes and pharmaceuticals, this uncharismatic but vital life form no doubt hold many more surprises in store for future research to discover. It's estimated that less than ten percent of all fungi species have so far been scientifically described; it's small wonder then that a recent study suggests an entirely new use for several types of these under-researched organisms.
Investigation of the Chernobyl nuclear power station in 1991 found that Cladosporium sphaerospermum, a fungus first described in the late nineteenth century, was thriving in the reactor cooling tanks. In other words, despite the high levels of radiation, the species was able to not only repair its cells but maintain a good rate of growth in this extreme environment. This led to research onboard the International Space Station at the end of 2018, when samples of the fungus were exposed to a month of cosmic radiation. The results were promising: a two millimetre thick layer of the fungus absorbed nearly two percent of the radiation compared to a fungus-free control.
This then suggests that long-duration crewed space missions, including to Mars, might be able to take advantage of this material to create a self-repairing radiation shield, both for spacecraft and within the walls of surface habitats. A twenty-one centimetre thick layer was deemed effective against cosmic rays, although this could potentially be reduced to just nine centimetres if the fungal mycelia were mixed with similar amounts of Martian soil. In addition, there is even the possibility of extracting the fungus' radiation-proof melanin pigment for use in items that require much thinner layers, such as spacesuit fabric.
If this sounds too good to be true, there are still plenty of technological hurdles to be overcome. Science fiction has frequently described the incorporation of biological elements into man-made technology, but it's early days as far as practical astronautics is concerned. After all, there is the potential for unique dangers, such as synthetic biology growing unstoppably (akin to scenarios of runaway nanobot replication). However, NASA's Innovative Advanced Concepts program (NIAC) shows that they are taking the idea of fungi-based shielding seriously, the current research considering how to take dormant fungal spores to Mars and then add water to grow what can only be described as myco-architecture elements - even interior fittings and furniture. In addition to the radiation shielding, using organic material also has the advantage of not having to haul everything with you across such vast distances.
Even more ideas are being suggested for the use of similarly hardy species of fungi on a Mars base, from bioluminescent lighting to water filtration. Of course, this doesn't take into account any existing Martian biology: the seasonal methane fluctuations that have been reported are thought by some to be too large to have a geochemical cause; this suggests that somewhere in the sink holes or canyon walls of Mars there are colonies of methane-producing microbes, cosily shielded from the worst of the ultraviolet. If this proves to be the case, you would hope that any fungi taken to the red planet would be genetically modified to guarantee that it couldn't survive outside of the explorer's habitats and so damage Martian biota. Humanity's track record when it comes to preserving the ecosystems of previously isolated environments is obviously not something we can be proud of!
What fungi can do alone, they also do in symbiosis with algae, i.e. as lichens. Various experiments, including the LIchens and Fungi Experiment (LIFE) on the International Space Station (incidentally, doesn't NASA love its project acronyms?) have tested extremophile lichens such as Xanthoria elegans and Rhizocarpon geographicum in simulated Martian environments for up to eighteen months. The researchers found that the organisms could remain active as long as they were partially protected, as if they were growing in sink holes beneath the Martian surface. Of course, this success also enhances the possibility of similar lifeforms already existing on the red planet, where it would have had eons in which to adapt to the gradually degraded conditions that succeeded Mars' early, clement, phase.
The CRISPR-Cas9 system and its successors may well develop synthetic fungi and lichens that can be used both on and especially off the Earth, but we shouldn't forget that Mother Nature got there first. Spacecraft shielding and myco-architecture based on natural or genetically modified organisms may prove to be an extremely efficient way to safeguard explorers beyond our world: the days of transporting metal, plastic and ceramic objects into space may be numbered; the era of the interplanetary mushroom may be on the horizon. Now there's a phrase you don't hear every day!
