An unassuming lichen harbors a hidden superpower: It’s remarkably immune to ultraviolet radiation. New experiments on the hardy organism name into query the long-held perception that alien planets bathed in ultraviolet mild should be sterile worlds, researchers report June 12 in Astrobiology. The invention might open up extra choices within the seek for life elsewhere within the universe.
Hundreds of exoplanets have been found up to now, however lots of them orbit a sort of small, extremely lively star apt to ship off blasts of energetic particles and radiation. And in contrast to our planet, these worlds seemingly don’t have ozone of their atmospheres. Ozone is fashioned from compounds produced by photosynthesis, and researchers haven’t discovered any proof of such a course of occurring on an exoplanet.
That’s been a fear, as a result of ozone, which consists of three oxygen atoms, features as a protecting blanket blocking the shortest-wavelength — and subsequently most damaging — ultraviolet radiation from reaching a planet’s floor. On Earth, hospitals use such radiation, often called UVC, to sterilize devices.
“It’s meant to kill life,” says Tejinder Singh, an astrobiologist at NASA’s Goddard Area Flight Middle in Greenbelt, Md.
Earlier work has proven that lichens, a symbiosis of algae and fungi, are remarkably immune to a barrage of powerful situations. However nobody had ever thrown excessive intensities of utmost ultraviolet mild at them for lengthy intervals of time to imitate the situations on an exoplanet, Singh says. “We pushed the bounds.”
In 2021 and 2022, Singh and his collaborators collected roughly half a kilogram of Clavascidium lacinulatum, a soil-dwelling lichen, from the Mojave Desert in southern Nevada. Again within the laboratory, the group uncovered the dark-colored lichen to UVC radiation.
After three months of publicity at intensities similar to these acquired on exoplanets, greater than 60 p.c of C. lacinulatum’s photosyntheticalgal cells have been nonetheless viable, the group discovered. “We couldn’t kill the lichen,” says Henry Solar, an astrobiologist on the Desert Analysis Institute in Las Vegas, Nev. and a member of the analysis group.
However roughly one minute in the identical situations was 100% deadly to Deinococcus radiodurans, a bacterium identified for withstanding radiation. And when the group remoted simply the lichen’s algal cells, they suffered the identical destiny as D. radiodurans.
Singh and his collaborators confirmed that C. lacinulatum incorporates chemical compounds that not solely block ultraviolet mild but in addition take away dangerous compounds often called free radicals produced by publicity to ultraviolet radiation.
Exoplanets blasted with ultraviolet mild subsequently aren’t essentially uninhabitable, the group concluded. Possibly an alien type of lichen might acquire a toehold in spite of everything.
An analogous situation additionally seemingly performed out nearer to residence way back, the researchers recommend. Earlier than our planet’s ozone layer developed, the earliest life would have wanted to resist UVC radiation, Solar says. “The situation that we’re hypothesizing really occurred on Earth billions of years in the past.”
These outcomes clearly reveal that C. lacinulatum is unusually immune to ultraviolet radiation, says Matthew Nelsen, a biologist on the Subject Museum in Chicago who was not concerned within the analysis. However the authors’ assertion that exoplanets bathed in ultraviolet mild may harbor comparable organisms is a little bit of a stretch, he says, since there are different stressors like temperature and water availability to contemplate. “I believe it’s untimely to say that lichens can survive on different planets.”
