Lichens can survive almost anything, and some might survive Mars
The symbiotic organisms appear to be able to avoid some radiation damage.
Whether anything ever lived on Mars is unknown. And the present environment, with harsh temperatures, intense radiation, and a sparse atmosphere, isn’t exactly propitious for life. Despite the red planet’s brutality, lichens that inhabit some of the harshest environments on Earth could possibly survive there.
Lichens are symbionts, or two organisms that are in a cooperative relationship. There is a fungal component (most are about 90 percent fungus) and a photosynthetic component (algae or cyanobacteria). To see if some species of lichen had what it takes to survive on Mars, a team of researchers led by botanist Kaja Skubała used the Space Research Center of the Polish Academy of Sciences to expose the lichen species Diploschistes muscorum and Cetrarea aculeata to simulate Mars conditions.
“Our study is the first to demonstrate that the metabolism of the fungal partner in lichen symbiosis was active while being in a Mars-like environment,” the researchers said in a study recently published in IMA Fungus. “X-rays associated with solar flares and SEPs reaching Mars should not affect the potential habitability of lichens on this planet.”
Martian ionizing radiation is threatening to most forms of life because it can cause damage at the cellular level. It can also get in the way of physical, genetic, morphological, and biochemical processes, depending on the organism and radiation level.
Going to extremes
Lichens have an edge when it comes to survival. They share characteristics with other organisms that can handle high levels of stress, including a low metabolism, not needing much in the way of nutrition, and longevity. Much like tardigrades, lichens can stay in a desiccated state for extended periods until they are rehydrated. Other lichen adaptations to extreme conditions include metabolites that screen out UV rays and melanin pigments that also defend against radiation.
Because the effects of UV radiation on lichens have been studied before, Skubała decided to focus on something that had not previously been explored, which is what happens to them when exposed to ionizing radiation while they are still metabolically active (lichens need water to keep their metabolism going). To do so, the researchers sprayed the lichens with water for hydration to keep them in a metabolically active state.
Each species spent five hours inside a dark chamber with simulated Martian conditions. This meant low pressure, low humidity, an “atmosphere” that was mostly carbon dioxide, and temperatures that started at a daytime 18° C (64° F), then plunged down to a nighttime minus-26° C (minus-14° F). X-ray radiation levels in the chamber were similar to those on the surface of Mars when there is strong solar activity, though solar flares and fluctuations in solar wind make actual Martian levels unpredictable.
I’m a survivor
When the lichens emerged from their simulated Martian habitat, both species were found to have retained some moisture despite a lack of humidity, so the researchers assumed that at least some metabolic activity was going on in both the fungal and photosynthetic components. Earlier, the photosynethic component of lichens had been tested during exposure to ionizing radiation, but not the fungal component.
Lichens that are not dehydrated are more prone to damage from ionizing radiation. Both fungal and algal cells in metabolically active lichens have repair mechanisms they can activate, but D. muscorum was much more resistant to the radiation than C. aculeata. This species suffered less oxidative stress, meaning that fewer reactive oxygen species built up in its cells. These unstable molecules contain oxygen and can severely damage cellular components and even lead to cell death.
Other adverse Martian conditions, such as an atmosphere dominated by carbon dioxide, can affect lichen metabolism but not completely shut it down. The fungal component needs oxygen so it can metabolize carbohydrates, but the metabolic processes of both species kept going even though there was little oxygen available. The researchers think it is also possible that the photosynthetic portion of the lichens might have produced oxygen that the fungal components could use.
Surprisingly, the process of photosynthesis was not that sensitive to X-rays in dark conditions. Fluorescence imaging measurements of chlorophyll concentrations showed that the photosynthetic component of D. muscorum remained undamaged throughout the experiment, while that in C. aculeata experienced a decrease in chlorophyll when exposed to X-rays. Both lichens were frozen after the experiment. When thawed, both became photosynthetically active again, with C. aculeata quickly regaining its initial chlorophyll levels.
Whether lichens can survive on Mars really depends on the species. Skubała thinks that further research is needed to determine all the features and adaptations that make them likely to survive in the face of intense ionizing radiation.
“Our findings lay the foundation for future studies, including long-term exposure experiments on the Mars surface,” she and her team said optimistically in the same paper. We haven’t yet intentionally landed an Earth organism on Mars, and it will likely be a long time before we can carry out an in situ experiment on the red planet.
Why D. muscorum was more effective at mitigating radiation damage is not completely known. After the experiment, concentrations of antioxidants (especially glutathione) were found to have increased during exposure. Glutathione can also limit cellular damage in humans and other organisms. It may help a lichen to survive ionizing radiation, but that doesn’t mean it can provide equivalent protection to us—we should think twice before we attempt to put boots on Mars.
IMA Fungus, 2025. DOI: 10.3897/imafungus.16.145477
Elizabeth Rayne is a creature who writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. She lurks right outside New York City with her parrot, Lestat. When not writing, she is either shapeshifting, drawing, or cosplaying as a character nobody has ever heard of. Follow her on Threads and Instagram @quothravenrayne.
