Titan haze distribution and optical properties retrieved from recent observations

• Published in: Icarus
• Main Authors: Rannou, Pascal, Cours, Thibaud, Le Mouélic, Stéphane, Rodriguez, S, Sotin, Christophe, Drossart, P, Brown, R.
• Other Authors: Groupe de spectrométrie moléculaire et atmosphérique (GSMA), Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique de Nantes UMR 6112 (LPGN), Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory Tucson (LPL), University of Arizona
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]; South Pole; polar night; South pole
• Online Access: https://u-paris.hal.science/hal-03657750; https://doi.org/10.1016/j.icarus.2010.03.016

International audience The VIMS instrument onboard Cassini observed the north polar region of Titan at 113°phase angle, 28 December 2006. On this spectral image, a vast polar cloud can be seen northward to 62°N, and elsewhere, the haze appears as the dominant source of scattering. Because the surface does not appear in the wavelength range between 0.3 and 4:9 lm, this spectro-image is ideal to study airborn scatterers both in methane bands and windows. In this work, we study this image, along with another image taken at 13°phase angle. This image probe both the atmosphere and the surface from pole to pole. First, we characterise the spatial distribution of the haze layer above 100 km between 80°S and 70°N. We find a north south asymmetry with a haze opacity increasing by a factor 3 from the south pole to the equator, then a constant value up to about 30°N and a decrease of a factor 2 between 30°N and about 60°N. Beyond 60°N, we can see the influence of the north polar cloud, even in the band, but no polar haze accumulation. The fact that the north polar region is still in the polar night is a possible explanation. No haze accumulation is observed in the southern polar region. Secondly, we partly identify the origin of spectral features in the 2:8-lm methane window, which are found to be due to deuterated methane ðCH 3 DÞ. This allows the analyse of this window and to retrieve the opacity of scatterers layer below 80 km (presumably made of aerosols and condensate droplets) between 35°N and 60°N. Finally, we constrained the values and the spectral behaviour of the imaginary part of the aerosol refractive index in the range between 0.3 and 4 lm. To do so, we studied the 2:8-lm window with the image taken at 113°phase angle. To complete the analysis, we studied the transmission through the haze layer in the 3:4-lm band observed in solar occultation mode with VIMS, and we analysed the single scattering albedo retrieved with DISR instrument between 0.4 and 1:6 lm. The imaginary part of the refractive index that we ...