Argentina: The 500-year-old Llullaillaco mummies (see “Diagnosis of Ancient Illness,” page 20) are remarkably preserved in part because they were buried in an extreme environment, inhospitable even to the microbes responsible for decomposition. The mummies piqued the interest of ecologists, who trekked up the volcano where they were found to study its microscopic ecosystem—a potential analogue for life on Mars. They found several unique varieties of fungi and microbes—extremophiles hanging on despite freezing temperatures, punishing UV rays, and almost no water.