Stretching from France in the west to Slovenia in the east, the Alps are Europe’s largest mountain range and – perhaps less famously – one of its largest continuous natural areas, far richer in biodiversity than the great majority of the continent.
Among other things, the mountain region is home to more than 3,000 species of lichen, those curious organisms formed by a symbiosis between a fungus and a photosynthesising creature such as green algae or cyanobacteria.
One of the most common Alpine lichens is Xanthoria elegans, shown above. Commonly known as the elegant sunburst lichen (for obvious reasons), the species grows on rocks, often near the perches of birds or rodents.
X. elegans is often used in lichenometry, a method for dating exposed rocks by the growth of lichens. A sample of X. elegans has also been taken to the International Space Station, where it survived 18 months of exposure to solar radiation, cosmic rays, vacuum, and extreme temperatures.