Scientists have finally discovered life in the heavens above—in the clouds, that is.
An analysis of hailstones recovered from a May 2009 storm has uncovered several different types of bacteria and organic materials that could potentially allow bacteria to survive in storm clouds.
"We found bacteria present and were able to tell where they were coming from," says Tina Santl-Temkiv, a researcher at Aarhus University in Denmark. She and her team found that many of the bacteria present came from plant surfaces. The organic materials found could have help sustain bacterial colonies and may have even allowed them to expand.
"Plant surfaces are hostile environments—bacteria are exposed to dry air and ultraviolet rays," she says. "Those are some of the same conditions found in the atmosphere, so maybe they're preadapted to surviving stressful conditions. We found more of them than we'd expect."
Studying life in clouds is tricky business: Looking for life in rain droplets isn't ideal because as it rains, the droplets pick up bacteria and other contaminants as it falls towards Earth. Aircraft used to sample clouds can potentially contaminate samples, and studying thunderstorm clouds is nearly impossible because of their violent nature.
That leaves hail, Santl-Temkiv says.
"Hail gets frozen in real time, so you can look at the conditions present in the cloud," she says. "When they're falling they also collect other bacteria, but we sterilized the surface and removed the outer layer before we studied it. Everything that's left comes from the cloud itself."
But finding hail can be difficult because of its often unpredictable nature. She says a friend called her during a particularly nasty storm and offered to pick up and freeze the 2-inch long hailstones.
"It was a really lucky thing," she says. Little research has previously been done on life inside hailstones.
Santl-Temkiv and her team believe that bacteria may travel long distances aboard clouds, allowing them to colonize new areas thousands of miles away after precipitation falls to the ground.
"I think it's now important that we look at different types of clouds," she says. "But sampling them is tough."