One of the most influential features of the atmosphere is most likely right before your eyes, floating in the air between you and your computer screen, hiding in plain sight.
The stuff we merely call dust has the power to change the face of Earth. It affects our climate and weather, alters the chemical and life processes in the oceans, distributes allergies and breathing problems, and, as people in Phoenix, Ariz., realized again this week, turns the sky dark enough to stop road traffic and air travel.
The great walls of dust that come rolling off the desert result from a conspiracy between the weather phenomenon of a powerful thunderstorm and the climate phenomenon of drought. They are known as haboobs, from the Arabic habb, the word for a downdraft wind.
Beyond such dramatic episodes, you can follow the footprints of dust from microscopic to global scales through a wide variety of climate and weather effects, from the warming and melting impact it has when it darkens the surface of snow and ice, the direct blocking of sunlight and visibility of the atmosphere, as well as the formation of rain.
So widespread is the influence of dust, in fact, that no single science or group of scientists has a complete understanding of it - a problem which a group of U.S. and British researchers describe this week in Eos, the weekly newspaper of the American Geophysical Union.
Geologist Gregory S. Okin of the University of California, Los Angeles, and colleagues write:
"Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated."
As a result, basic research questions about the formation of dust, the processes that make it airborne - or keep it on the ground - are not very well understood. The authors call on scientists interested in the subject to get their heads in the clouds and come up with a comprehensive approach.
IMAGE: Thick dust blew off the coasts of Sudan and Eritrea in early July 2011. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this natural-color image on July 12, 2011.