Rain and lightning
Rain on Venus
As a point of interest, it should be noted that the frequent sulphuric acid rain showers on Venus never reach the surface of the planet. Falling from the cloud layer between 48 and 58 km, these acid droplets will encounter such high temperatures at 30 km that they evaporate. Sulphuric acid evaporates at about 300°C ; decomposing into water and sulphur dioxide. These gases then rise to feed the clouds. Contrary to what one might think, acid rain on Venus is therefore not a major cause of surface erosion.
Lightening on Venus
The Pioneer-Venus probe recorded almost permanent rumbles caused by the thickness of the Venus atmosphere that increases the sound propagation. These were interpreted as the proof of the existence of thunder on Venus.
However, when the Cassini-Huygens probe performed 2 Venus flybys before leaving for Saturn, it recorded all emissions coming from Venus to try and detect electrical discharge. But nothing was detected. Three hypotheses are currently proposed:
Scientists are not surprised by the absence of lightning. Electrical discharges are caused by vertical movements of cloud mass. However, the atmospheric circulation on Venus occurs in a horizontal direction.