• The International Space Station often hosts a number of trays attached to the exterior of the spacecraft. Inside the trays are various substances: bacteria, algae, fungi, tardigrades, and so on. They are there to see if they can survive exposure to the harsh conditions and cosmic rays of space. So far, the best survival rate has been found in lichens.
• Lichens are a symbiotic relationship between algae and fungus. A German botanist coined the term “symbiosis” in 1877 specifically to describe the partnership involved in lichens.
• With lichens, algae provide energy produced through photosynthesis, while the fungus breaks down the minerals of the rock that the lichen is attached to, providing nutrition.
• Lichens cover about 8% of the land area of the planet, more than is covered by tropical rainforests. They cling to all sorts of surfaces ranging from roofs, gravestones, and fences to cliffs, trees, and the surface of deserts.
• There are over 20,000 species of lichens worldwide. In the Arctic, there are about 2,000 species of lichen. Even in Antarctic, there are about 400 species. The slowest growing plant on the planet may be a lichen on rocks in the Arctic where it gets colder than -90 F (-68 C) in the winter. Lichen one inch in diameter may be 1,000 years old.
• A single common English Oak tree growing in a temperate climate was found to be supporting 324 different species of lichen.
• Lichens deteriorate surfaces by prying small cracks apart by the force of their growth, and by secreting acids that dissolve solid rock to be digested. When lichens die, they decompose and provide the first bits of soil in harsh ecosystems. Lichens turn inanimate minerals into a form that other creatures can use.
• In 2006, the faces of the presidents on Mount Rushmore were cleaned with a pressure hose in order to remove over six decades worth of lichen growth. In 2019, locals on Easter Island began scrubbing the lichens off the stone heads the island is famous for.
• In space, the harsh conditions dehydrate lichens almost immediately, forcing a state of dormancy. The temperatures on the exterior of the space station vary between -184F (-120 C) to 248F (120 C) and back again all within a few hours.
• The first attempt to send lichens into space ended with an unmanned Soyuz rocket crash-landing seconds after liftoff from a Russian launching pad in 2002. Months later, when the snow melted enough to retrieve the wreckage, the lichens were still alive.
• Lichens can be reconstituted after being in a state of dehydrated dormancy for ten years.
• Radiation will kill lichens but it must be administered in phenomenal doses. When irradiated with 12,000 times the dose required to kill a human, lichens were unphased. When the dose was doubled, their ability to reproduce was impaired, though they continued to live.
• The word “lichen” comes from the Greek verb “leichein” meaning “to lick up” because they seem to lick their way across the ground.
• There are 108 different species of lichen growing on Stonehenge in England. Some of the species only grow in maritime environments, meaning that either they were on the stones already when they were transported from the sea, or that the salt sea breeze is occasionally strong enough to bring the spores in from 30 miles (48 km) away.
• One researcher runs an institute called “Ways of Enlichenment.”
