High concentration of bacteria in center of hailstones

Science Daily: Researchers have discovered a high concentration of bacteria in the center of hailstones, suggesting that airborne microorganisms may be responsible for that and other weather events…. "Bacteria have been found within the embryo, the first part of a hailstone to develop. The embryo is a snapshot of what was involved with the event that initiated growth of the hailstone," says Alexander Michaud of Montana State University in Bozeman, who presented the research.

Michaud and his colleagues analyzed hailstones over 5 centimeters in diameter that were collected on the University campus after a storm in June 2010. The large hailstones were seperated into 4 layers and the meltwater from each layer was analyzed. The number of culturable bacteria was found to be highest in the inner cores of the hailstone.

"In order for precipitation to occur, a nucleating particle must be present to allow for aggregation of water molecules," says Michaud. "There is growing evidence that these nuclei can be bacteria or other biological particles."

Michaud's research is part of a growing field of study focusing on bioprecipitation, a concept where bacteria may initiate rainfall and other forms of precipitation including snow and hail. The formation of ice in clouds, which is necessary for snow and most rainfall events, requires ice nuclei (IN), particles that the ice crystals can grow around….

A field of hailstones shot by Soon Chun Siong, uploaded by Nerdybeng at en.wikipedia