Lichen samples exposed to six kilograys of gamma irradiation—six times the standard dose for food sterilization in the United States and twelve thousand times the lethal dose for humans—were entirely untroubled. When the dose was doubled to twelve kilograys—two and a half times the lethal dose for tardigrades—the lichens’ ability to reproduce was impaired, although they survived and continued to photosynthesize with no apparent problems.
