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Séminaire du Jeudi 8 Novembre 2012

Molecular growth in planetary atmospheres : Recent developments from Titan and extrasolar giant planets

Panayotis Lavvas (U. Reims)
Thursday 8 November - 11 h 00
Salle Manuel Forestini - IPAG

Photochemical processes allow the formation of increasing complexity molecular structures. Depending of the chemical potential of each environment this process can eventually proceed to the production of large enough molecular structures that start to behave as particles, following the laws of microphysical evolution (photochemical aerosols).

Saturn’s largest moon, Titan, provides us a unique opportunity to study the atmospheric molecular growth and the mechanisms affecting it. The ubiquitous aerosols observed in this atmosphere are the result of the molecular growth that starts in the ionosphere and gradually evolves as the particles sediment towards the surface. We will see how recent measurements from the Cassini spacecraft provide us insight to the transition region between molecular growth and aerosol formation and reveal the role of electrostatic charging in the process.

Photochemical aerosol are also observed in the atmospheres of the giant planets of our solar system, while current observations suggest that they are also present in the atmospheres of extrasolar giant planets. Hence, AMG is an active process at both high and low temperatures. Extending though the mechanisms identified in our solar system to the cases of exoplanets requires a good understanding of the chemical composition of these environments. We will see how we can interpret the thermospheric observations of Si in HD209458b and what conclusions can be derived for the chemical complexity of similar environments.

Slides in PDF format


Sous la tutelle de:

tutelles

Sous la tutelle de:

CNRS Université Grenoble Alpes