How did that contrail get there?
Contrails are clouds formed when water vapor condenses and freezes around small particles (aerosols) that exist in aircraft exhaust. Some of that water vapor comes from the air around the plane; and, some is added by the exhaust of the aircraft. They are the most obvious human-induced clouds around the globe. Other types of clouds are formed by water vapor that condenses on particles which are present in the atmosphere due to many sources, such as from volcanoes or dust storms, not specifically from aircraft exhaust. For a neat ID chart on contrails check out our Contrail Education site at: http://asd-www.larc.nasa.gov/GLOBE/ and click on Resources. You can also click on Contrail gallery to see other great photos of contrails.
