A recent study published in Astrobiology reveals that life may be able to survive on Earth-like exoplanets, even under intense solar radiation. Researchers found that lichen from the Mojave Desert endured three months of exposure to radiation levels previously thought to be deadly. Although the lichen (Clavascidium lacinulatum) was damaged, it recovered and replicated, suggesting photosynthetic life could exist on planets with harsh solar conditions.
The study was inspired by an observation made by Henry Sun, a microbiologist at the Desert Research Institute (DRI). Noticing that desert lichens were black instead of green, he discovered they contained a natural pigment acting as a powerful sunscreen. This adaptation allows them to withstand ultraviolet (UV) radiation that would typically be lethal.
On Earth, life has evolved to tolerate UVA and UVB rays, but UVC – the most harmful wavelength – is blocked by the atmosphere. UVC is so destructive that it is used for sterilization, as even brief exposure can damage DNA and prevent reproduction. However, many exoplanets orbit M and F-type stars, which emit high levels of UVC radiation, raising doubts about their habitability.
To test survival under extreme conditions, Sun and his team collected lichen from the Mojave Desert and exposed it to UVC radiation in a lab for three months. Remarkably, half of the algal cells remained viable and reproduced when rehydrated. Further analysis revealed that lichen acids act as a natural UV shield, similar to additives in UV-resistant plastics. When separated from their protective fungal layer, the algal cells died within seconds under UVC exposure.
Interestingly, this adaptation appears unnecessary on Earth, as UVC is already filtered by the atmosphere. The lichen’s protection likely evolved as an extension of its defense against UVA and UVB. Additional tests in oxygen-free environments showed even greater resilience, suggesting atmospheric chemistry plays a role in radiation damage.
The findings imply that exoplanets with extreme radiation could still host microbial life. As the researchers note, these worlds might be “teeming with colonial microorganisms” that, like Mojave lichens, are naturally shielded from UVC stress. This discovery expands the potential for finding life beyond our solar system.
For more details, visit DRI.