Discovery News: New satellite imagery has mapped the concentration and movement of aerosols in the atmosphere over North America. Aerosols are tiny dust particles produced from natural processes such as volcanic eruptions and from human-caused pollution such as coal-burning. In the low atmosphere, they can cause human health issues; at higher altitudes, they absorb heat, reflect sunlight, and affect cloud formation and precipitation. Approximately half of the aerosols floating over North America originate from Asia and elsewhere, a fact that surprised Lorraine Remer, an aerosol scientist at the University of Maryland, Baltimore County. The majority of the foreign particles were found mainly in the upper atmosphere and consisted of dust swept up by desert winds. Just what impact that dust has on global climate patterns and climate change is not yet certain, but the mapping of its concentration and movements is the first step in finding out.