Venus clouds composition
Another essential characteristic of Venus’ atmosphere is the thick cloud layer that covers the planet, extending from 30 to 90km, which has noticeable stratification that is surprisingly stable.
The upper layer
Between 70 and 90km high is a cold region with a fog of aerosols smaller than a micrometre, particularly over the polar regions.
The main layer
With a base at 47 kilometres, the main layer is divided into three sub-layers and composed of fine droplets of sulphuric acid in an aqueous solution. This is generally 75% sulphuric acid (H2SO4) and 25 % water (H2O), of which the particle size distribution has several modes: 2 or 3 depending on the sub-layer, corresponding to typical particle sizes of 0.1, 1 and 10 micrometres.
Chloride compounds (maybe FeCl3) are probably present at altitudes below 60 kilometres.
Below the main layer
One finds a tenuous fog that extends down to 30 kilometres.