In This Issue

#### Ancient microbes in a salty, ice-sealed Antarctic lake Antarctica’s Lake Vida. Antarctica’s Lake Vida, which is five times saltier than seawater and permanently covered by more than 20 m of ice, represents one of the least hospitable ecosystems on Earth. Using sanitary procedures and equipment, Alison Murray et al. (pp. 20626–20631) removed cores of ice from the frozen lake, collected samples of the brine in the lake ice, and assessed the brine’s potential for sustaining life. Previous studies of Lake Vida indicate that the brine has been isolated from the surface environment for at least 2,800 years. Despite the cold, dark, and isolated nature of the ecosystem, the authors found that the brine harbors a diverse assemblage of metabolically active bacteria. The authors report that the brine is oxygen-free, slightly acidic, and contains very high levels of organic carbon, molecular hydrogen, as well as oxidized and reduced compounds—an unusual finding considering the brine has been isolated from external sources of energy for millennia. Geochemical analyses suggest that chemical reactions between the brine and the underlying sediment generate nitrous oxide and molecular hydrogen, the latter of which may in part provide the energy needed to support the brine’s microbes. The findings shed light on the limits to life in extreme environments on Earth and other icy planets, according …