Lichens thrive in Martian simulation, another step towards life on Mars

A recent experiment has shown that certain lichen species can remain metabolically active in an environment similar to that found on Mars. The study challenges assumptions that Mars is entirely inhospitable, highlighting the life’s adaptability under extreme conditions.

This research, published in the open-access journal IMA Fungus, demonstrates that lichens can function despite exposure to high levels of ionizing radiation and other harsh factors that characterize the planet’s surface. 

The discovery builds on prior findings suggesting that some microorganisms can endure environments analogous to Mars, but this is the first time the metabolic activity of the fungal component in lichens has been observed under such conditions. 

In this study, the focus centered on two lichen species, Diploschistes muscorum and Cetraria aculeata.

The researchers found that the former was especially able to continue its metabolic processes and resistance mechanisms despite exposure to doses of X-ray radiation and temperatures reflecting extremes on Mars.

Lichens accept the Mars challenge

Mars has captivated scientists for centuries, primarily because it is the most Earth-like planet in our solar system.

Yet its thin atmosphere, lack of a global magnetic field, and the resulting bombardment of radiation make the Martian surface an extreme and potentially lethal environment for most known life-forms. 

Temperatures can fluctuate widely, and intense ionizing radiation – particularly during periods of heightened solar activity – is considered a principal threat to any organisms that might attempt to exist there.

Despite these obstacles, researchers have gradually gathered evidence suggesting that some terrestrial extremophiles may find ways to cope with the Red Planet’s challenging conditions. 

This latest study takes that line of reasoning one step further, revealing that lichens – a symbiotic partnership between fungi and photosynthetic organisms – have a surprising capacity for survival and metabolic activity in simulated Mars-like conditions.

Understanding lichens – the basics

Lichens are remarkable organisms formed through a symbiotic partnership between a fungus and an alga or cyanobacterium.

The fungus provides structure and absorbs moisture and minerals from the environment, while the algal or bacterial partner produces food through photosynthesis.

Together, they create a highly adaptable organism capable of surviving in some of the harshest environments on Earth – from tree bark and rocky cliffs to deserts and polar regions. They don’t require soil to grow and can thrive with minimal resources.

What makes lichens especially fascinating is their resilience and ecological value.

Many species grow extremely slowly, sometimes only a few millimeters per year, yet they can live for decades or even centuries. Scientists often study lichens to monitor air quality, as some species are highly sensitive to pollutants.

Though they may appear simple, lichens play an important role in ecosystems and continue to offer insight into the complexities of symbiotic life.

Exposing lichens to Mars-like conditions

In the new study, scientists exposed Diploschistes muscorum and Cetraria aculeata lichen species to a mixture of factors replicating what might be encountered on Mars. 

These factors included a rarefied atmospheric pressure, temperatures that could dip and rise in short order, a Mars-like gas composition, and X-ray radiation on par with what would be expected over a year of strong solar activity. 

The experts ran this experiment for five hours, then looked at whether the fungal component of the lichen remained metabolically active.

Could lichens survive on Mars?

The results indicated that D. muscorum was particularly adept at coping with these trials. According to the team, this species managed to carry out essential biochemical functions despite being subjected to Mars-like conditions.

The fungus also showed clear signs of triggering defense mechanisms to mitigate the harmful effects of ionizing radiation.

“Our study is the first to demonstrate that the metabolism of the fungal partner in lichen symbiosis remained active while being in an environment resembling the surface of Mars,” Kaja Skubała, team leader explained.

“We found that Diploschistes muscorum was able to carry out metabolic processes and activate defense mechanisms effectively.”

Exploring radiation survival

Ionizing radiation poses a grave danger for any organism lacking robust protective strategies or the ability to repair damage to cellular components.

The research team specifically scrutinized whether high levels of X-ray radiation would effectively halt metabolic activity. 

Previous assertions held that a steady stream of intense radiation from the Sun and cosmic sources might render the Martian surface permanently sterile.

Yet in this experiment, the fungal partner was clearly able to maintain function, offering insight into how certain organisms might defy radiation-related stress.

These findings expand our understanding of biological processes under simulated Martian conditions and reveal how hydrated organisms respond to ionizing radiation – one of the most critical challenges for survival and habitability on Mars.

Ultimately, this research deepens our knowledge of lichen adaptation and their potential for colonizing extraterrestrial environments.

What happens next?

By establishing that lichen fungi can endure – and remain active – amid Mars-like conditions, the study opens new doors for astrobiology.

It challenges the belief that Mars’s radiation exposure alone is an insurmountable barrier for life, prompting further investigations into how multiple species of extremophiles might cope with the various hazards of the Martian environment.

“The findings call for longer-term studies that examine how chronic exposure to radiation influences lichens and other organisms, as well as how they might adapt or evolve when subjected to such stressors for months or even years,” Skubała concluded.

Understanding these processes could be integral not only for unearthing ancient life on Mars (if it ever existed) but also for potentially selecting candidate species that could be used in experimental greenhouses or bio-based life-support systems during future crewed missions to the Red Planet.

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The full study was published in the journal IMA Fungus.

Image Credit: Cetraria aculeata, a species of lichens, superimposed on Mars. Credit: Lichen: Skubała et al. Design: Pensoft Publishers.

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