SSS 2008-02-29

（单词翻译）

This is Scientific American's 60-Second Science. I'm Karen Hopkin, this'll just take a minute.

Next time you are shoveling snow off your walk, don't blame the weatherman, blame bacteria. Because an international team of scientists has found that microbes that float through the atmosphere can seed the formation of ice crystals in clouds, crystals that then precipitates¹ snow. The discovery subscribed² in the February 29 issue of Science. Some bacteria including bugs³ that infected plants have been known to catalyze⁴ the growth of ice here on earth. So the scientists got to wondering whether they might do the same in the sky. Making atmospheric  ice crystal is the first step in any recipe for precipitation whether the final dish is rain or sleet⁵ or snow. So the scientists collected fresh snow from various places around the world including the French Alps and Antarctica and Bozeman, Montana. They found that most of their samples contained cells and cell fragments and these biological materials were capable of nucleating the growth of ice. How the bugs got there in the first place is anybody's guess. The scientists figure microbes may drift thousands of miles before they get caught up in a cloud and scare up a storm. Just something to ponder next time you stick out your tongue to catch a pretty snowflake.

Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.