Titan

… is Saturn’s largest moon and the only moon in our solar system with a substantial atmosphere as well as large liquid reservoirs at its surface.

Major steps in our understanding of Titan took place with the CassiniHuygens mission to the Saturnian system.

In many ways Titan resembles the terrestrial planets and particularly Earth, as it is the only other body in our solar neighborhood with liquid reservoirs at its surface. In this world, the familiar to us role of water in our atmosphere, is replaced by methane (CH4), which at the extremely low temperature conditions at the surface (94 K ≈ -180oC), survives as a liquid.

Methane along with nitrogen (N2) are the main components of Titan’s atmosphere. Like for Earth, Titan’s atmospheric nitrogen is far more abundant than any other species and constitutes the bulk of the atmosphere, while methane only corresponds to a few percent of the atmospheric mass, followed by smaller abundances of H2 and CO. Although seemingly small, methane allows for the production of a very complex inventory of organic molecules. This process starts with the braking up of CH4 by solar photons followed by reactions among the dissociation products and methane, which form larger hydrocarbons such as ethane (C2H6), ethyle (C2H4), and acetylene (C2H2). In their turn these second order hydrocarbons are dissociated by photons, and further interactions of their photolysis products with the rest of the gas phase background leads to the production of even larger molecules. This procedure proceeds perpetually and is further enriched by the photolysis products of N2 and CO. Actually Titan is the most active organic laboratory of our solar system!

Eventually all these complex organic species lead to the formation of aerosol particles in Titan’s atmosphere. These are so abundant that they completely enshroud the whole moon, giving it its orange-brown hue (see image above captured by the Huygens prode, credit: JPL, University of Arizona). My research in this world focuses on the physical and chemical processes that define the formation and evolution of these aerosols, as well as their role in the evolution of Titan’s atmosphere.

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