context1: The polar upper troposphere and mesosphere are extremely dynamic; large bright <strong>clouds</strong> may appear and disappear over the space of a few hours. One such event was observed by Venus Express between 9 and 13 January 2007, when the south polar region became brighter by 30%. This event was probably caused by an injection of sulfur dioxide into the mesosphere, which then condensed forming a bright <strong>haze</strong>.
context2: The system generates smoke by vaporizing medium viscosity oil in a specially designed exhaust manifold. The hot vapors form a thick, white <strong>cloud</strong>. Other components may be added to the oil to form different types of cloaking <strong>hazes</strong>.