Frigid, slim on nutrients, and bombarded by ultraviolet rays, clouds are about the last place on Earth scientists would look for life. Yet Birgit Sattler, a limnologist at the University of Innsbruck in Austria, has discovered bacteria that are not just surviving but thriving in the cumulous zone.
Sattler identified the bugs after a colleague sent her some cloud samples collected and frozen onto Teflon plates set up atop Mount Sonnblick, near Salzburg, Austria. Even at subfreezing temperatures, the bacteria could take up radioactively tagged amino acids and DNA bases. This indicates the microbes were still growing and reproducing. They may be surviving on protein-rich pollen grains, Sattler says, as well as on leaf particles and microscopic oil droplets that float upward. She thinks they may convert the oil into alcohol for use as their own antifreeze.
Lofty bacteria could influence climate by acting as nuclei around which rain droplets form. In addition, Sattler says, finding bacteria in clouds suggests that life could exist in similarly extreme surroundings on alien planets. "Why not? I've done research in glaciers, Antarctic lakes, and in Alpine ice, but this is the most extreme habitat in which I've found bacteria," she says. "If anything happens to Earth, bacteria will survive."