14 research outputs found
The evolution of Titanâs high-altitude aerosols under ultraviolet irradiation
International audienceThe CassiniâHuygens space mission revealed that Titanâs thick brownish haze is initiated high in the atmosphere at an altitude of about 1,000âkm, before a slow transportation down to the surface. Close to the surface, at altitudes below 130âkm, the Huygens probe provided information on the chemical composition of the haze. So far, we have not had insights into the possible photochemical evolution of the aerosols making up the haze during their descent. Here, we address this atmospheric aerosol aging process, simulating in the laboratory how solar vacuum ultraviolet irradiation affects the aerosol optical properties as probed by infrared spectroscopy. An important evolution was found that could explain the apparent contradiction between the nitrogen-poor infrared spectroscopic signature observed by Cassini below 600âkm of altitude in Titanâs atmosphere and a high nitrogen content as measured by the aerosol collector and pyrolyser of the Huygens probe at the surface of Titan