The question of whether life ever existed on Mars remains an enigma, particularly given the planet’s harsh environment marked by extreme temperatures, intense radiation, and a thin atmosphere that complicates the prospects for habitability.
Yet, the resilience of extremophiles on Earth, particularly lichens, has led scientists to explore their potential for survival on the red planet.
Lichens are unique organisms formed through a symbiotic relationship between fungi and photosynthetic partners such as algae or cyanobacteria. Recent research led by botanist Kaja Skubała from the Space Research Center of the Polish Academy of Sciences aimed to examine whether certain lichen species could withstand Martian-like conditions.
In a groundbreaking study published in IMA Fungus, the researchers investigated how two specific lichen species, Diploschistes muscorum and Cetrarea aculeata, would respond when exposed to an environment resembling Mars.
This study marks the first time that scientists have demonstrated the metabolic activity of the fungal component in lichen symbiosis while subjected to conditions simulating planet Mars.
Skubała and her team found that X-rays generated by solar flares in space should not significantly reduce the potential for lichens to thrive on Mars.
Martian environments are hostile to most forms of life, primarily due to ionizing radiation that can hinder critical cellular processes.
However, lichens possess several advantages that enhance their survival prospects.
This includes their ability to maintain a low metabolism, requiring minimal nutrition, and having substantial longevity.
Like tardigrades, lichens can enter a desiccated state, allowing them to survive extended periods of drought until moisture returns.
Furthermore, lichens have biological adaptations that help them withstand UV radiation, including specific metabolites that filter harmful rays and melanin pigments that provide protection against radiation damage.
Skubała’s research specifically focused on a previously unexplored aspect of lichen biology: the effects of ionizing radiation on the fungal component while the lichen is in a metabolically active state.
To simulate the Martian environment, the researchers hydrated the lichens with water, allowing metabolic processes to continue during the experiment.
Both lichen species were placed in a dark chamber for five hours under conditions mimicking the surface of Mars, which included low atmospheric pressure and humidity, a carbon dioxide-rich atmosphere, and temperature gradients ranging from 18°C (64°F) by day to minus-26°C (-14°F) by night.
Additionally, the radiation levels inside the chamber were equivalent to those experienced on Mars during periods of high solar activity, albeit with the understanding that actual Martian radiation levels can vary due to solar flares and fluctuations in solar wind.
After the experiment, it was observed that both lichen species retained some moisture despite the extremely low humidity, suggesting ongoing metabolic activity in their fungal and photosynthetic components.
Prior research had already examined the impact of ionizing radiation on the photosynthetic aspects of lichens, but not on the fungal parts until now.
While metabolically active lichens are more susceptible to ionizing radiation, the study revealed that Diploschistes muscorum exhibited significantly greater resistance compared to Cetrarea aculeata.
This advantage was evidenced by lower levels of oxidative stress in D. muscorum, indicating fewer reactive oxygen species in its cells, which can be harmful and lead to cell death.
Moreover, adverse conditions on Mars, such as the atmosphere rich in carbon dioxide, could disrupt lichen metabolism without entirely halting it.
Although the fungal component relies on oxygen for carbohydrate metabolism, it appears that both lichen species could continue their metabolic activities even in the face of low oxygen availability.
The researchers hypothesized that the photosynthetic portion may have generated some oxygen during the experiment, providing additional resources for the fungal component to utilize.
Interestingly, the photosynthesis process in D. muscorum remained largely unaffected by X-ray exposure in dark conditions.
Fluorescence imaging revealed that chlorophyll levels in D. muscorum remained stable throughout the experiment, whereas C. aculeata showed a decline in chlorophyll concentrations when exposed to X-rays.
Encouragingly, both species were immediately frozen after the experiment. Upon thawing, both lichens were able to resume photosynthetic activity, with C. aculeata quickly recovering its chlorophyll levels.
The capacity for lichens to endure Mars-like conditions likely varies by species, prompting Skubała and her team to emphasize the necessity for further studies to identify the specific traits and adaptations that influence their survival against intense ionizing radiation.
“Our findings lay the foundation for future studies, including long-term exposure experiments on the Mars surface,” Skubała expressed optimistically in the published paper.
Despite the current inability to land Earth organisms on Mars intentionally, researchers remain hopeful about conducting in situ experiments on the planet in the future.
An intriguing question arises regarding why D. muscorum was more adept at mitigating radiation damage. During experimentation, concentrations of antioxidants, especially glutathione, increased, leading researchers to speculate that this compound may enhance a lichen’s ability to withstand ionizing radiation.
However, while glutathione may help lichens navigate radiation exposure, it should not be misconstrued as a protective measure for humans, urging caution against premature plans for human exploration of Mars.
The study of lichens opens up new avenues in our understanding of potential life on Mars while highlighting the remarkable adaptability of these organisms in the face of challenging environments.
image source from：https://arstechnica.com/science/2025/04/lichens-can-survive-almost-anything-and-some-might-survive-mars/
