Aerosols are small liquid or solid particles in suspension in a gas. Solid smoke particles from the burning of vegetation, dust formed by wind erosion of soil, or liquid droplets produced by the ocean waves are examples of aerosols.
Aerosols are present in many planetary environments, for example, in the atmospheres of Mars, the giant planets, and Titan, and they were probably present in the primitive atmosphere of the Earth, much as they are presently. Atmospheric aerosols can play an important role in climate, producing an antigreenhouse effect, like the haze in Titan’s atmosphere. Atmospheric photochemistry in several extraterrestrial environments, like Titan, produces organic aerosols which are similar to laboratory-synthesized tholins, which can produce a complex set of prebiotic chemicals when reacted with water.