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Watch a cloud being born

If you’ve ever looked up and seen thin, wispy clouds, you’ve probably seen cirrus clouds. Now, scientists have captured the creation of a cirrus cloud by modifying an environmental scanning electron microscope (ESEM)—a microscope that can magnify subjects in a gaseous environment. They added a new chamber to give the instrument the capacity to accurately produce specific temperature, pressure, and relative humidity conditions where one particular cloud type should form. To see how cirrus clouds form, scientists placed the makings of a cloud in the modified ESEM chamber: mineral particles and water vapor. At the temperature, pressure, and relative humidity where cirrus clouds form 6000 meters above Earth, the particles attracted water vapor that froze on their surfaces, creating the first ice crystals that would be present in a baby cirrus cloud. The researchers, who published their work in Physical Chemistry Chemical Physics, captured an image every 3 seconds during this process and put them together in time-lapse videos (above), where crystals form on particles just 50 nanometers wide. They also note that their modified ESEM is a jump forward toward more fully understanding how cloud formation affects Earth’s climate.