Lichens as Astrobiological Models: Experiments to Fathom the Limits of Life in Extraterrestrial Environments

Abstract

Amongst extremophiles on Earth, lichens are one of the most resistant forms of life to harsh terrestrial environments, as well as some bacteria, cyanobacteria, cryptoendolithic communities, and lithic fungi. Many lichens species are well known as survivors under the most stressful environments, capable of coping with harsh climatic conditions, including extreme ranges of temperature, radiation and humidity. Lichens combine in a single, compact and long-term living system, the heterotrophic and autotrophic paths of life. Consequently, space simulation and space exposure experiments have focused on these complex organisms, demonstrating their high capacities of survival and recovery and becoming valuable models in astrobiological research to fathom the limits and limitations of terrestrial life. These experiments will contribute to the comprehension of the effects of space and planetary environment on biological systems for future human exploration, as well as deepen our knowledge on the limits, distribution and origin of life.