A suspension of droplets or particles in a gas; more precisely, of particles with a maximum diameter of 1 μm (fog and mist are thus aerosols). In meteorology, the term is often used to describe the particles suspended within the air, such as minute fragments of sea-salt, dust, organic matter, and smoke. These enter the atmosphere by natural processes such as vulcanicity, and by human agency such as burning fossil fuels. Aerosols absorb heat and may act as condensation nuclei. NASA posts a daily global aerosol map on the web.