EPSC2021: From walls and railings of our cities to…space: the story of Xanthoria parietina

One of the main topics in astrobiology is the study of life limits in stressful environments -very high temperatures, inhuman pressures, deadly radiations- in order to shed light on the possibility of life in space or in extra-terrestrial habitats such as Mars. You might think it’s difficult to find life forms suitable for these studies, but instead in some cases they are very common; so common as to grow on walls and railings of our cities. 

This is precisely the case of Xanthoria parietina, a yellow-orange leafy lichen selected by the research group of Dr John Robert Brucato, Senior Research Scientist at INAF, the Italian National Institute of Astrophysics, for their study presented at EPSC2021.

“The Xanthoria parietina is so common in our cities because it is particularly tolerant to air pollutants as nitrogen oxides and heavy metals” says John, “but we chose it for its ability to produce a particular substance, the parietin, which allows it to protect itself from UV rays”.

In the study, presented at EPSC by Christian Lorenz, a Master’s Student in Environmental Biology at the University of Florence, John and his team tested the lichen under simulated UV space radiations in two different extreme and dehydrating environments, i.e. in nitrogen atmosphere and in vacuum, and demonstrated that it was able to survive. 

“The innovative aspect of our study is the spectroscopic analysis we used.” says Christian. “This analysis allowed us to obtain for the first time the spectrum of this lichen species, which we monitored during the exposure, allowing us to appreciate the real time changes in it.”

Is this silent inhabitant of our cities ready to colonise space? John thinks it’s too early to tell: “As the next step of our study, we will directly assess the presence of damages in the lichen through electron microscope analyses and expose it to other extreme conditions. Then, it would be really exciting to expose it in real space conditions, for example on the ISS!”.

For more information about the work, you can have a look at Christian’s presentation, Survival of Xanthoria parietina in simulated space conditions: spectroscopic analysis and vitality assessment during the EPSC2021 session TP5 on Friday 17 September.