SO Colloquium – The formation of high-altitude clouds on terrestrial planets
The three rocky planets in the inner Solar System, Mars, Venus and Earth, host many types of clouds. In particular, the highest-altitude clouds forming up to 100 km above the surface are the most intriguing ones, as they form at the edge of space and are rarely visible to the human eye.
On the Earth, the middle atmosphere hosts a sulphuric acid aerosol layer and clouds formed of water ice. Both carbon dioxide ice and water ice clouds form in the Martian atmosphere. Venus is covered in a thick sulphuric acid cloud layer, but above that, water or carbon dioxide ice clouds might form in certain conditions. In addition to the necessary ingredient in the form of a condensable vapour, one of the keys to cloud formation is pre-existing particles called condensation nuclei.
Planet surfaces provide a good source of particles (such as mineral dust, biogenic aerosols, sea salt, pollution). However, particles from a surface source cannot reach very high altitudes in large amounts and thus another source, such as meteorites, is required in the middle atmosphere. This presentation will provide an overview of the recent advances on high-altitude cloud formation on the three planets, and show some images of the thin high-altitude clouds we actually can see. It will also discuss links between the processes and highlight the remaining open questions.
Fecha y lugar: 26/03/2026 – 12:30 | Salón de Actos
Anni Määttänen
LATMOS laboratory, Centre national de la recherche scientifique (CNRS)