The Soviet probes that were sent to land on Venus were equipped with artificial lighting, in case the thick cloud cover of the planet prevented much illumination from reaching the surface. The light there, however, proved to be more than adequate for returning images of the rocky terrain. This indicated that the lower atmosphere is clear. A relatively clear layer lies above this one. These are relatively gentle, but they are still strong enough to move sand-size particles around.
Faster winds exist at higher altitudes in the atmosphere.
This is called the superrotation of the atmosphere. A number of the Venus probes have made measurements that have been interpreted as indicating lightning activity in the planet's atmosphere. Scientists have assumed that the geologies of Venus and Earth should be fairly similar. The reasoning behind this is that the heat that drives geological activity is generated mostly by the decay of radioactive elements, so that the amount of geological activity that a planet exhibits is believed to increase with increasing size. Thus the similarities in mass, size, and probable overall composition of Venus and Earth would indicate that the planets would have similar rock compositions and surface geology as well.