HST spectral imaging of Titan's haze and methane profile between 0.6 and 1 μm during the 2000 opposition

Abstract

We report on the analysis of high spatial resolution visible to near-infrared spectral images of Titan at L s = 240 ° in November 2000, obtained with the Space Telescope Imaging Spectrograph instrument on board the Hubble Space Telescope as part of program GO-8580. We employ a radiative transfer fractal particle aerosol model with a Bayesian parameter estimation routine that computes Titan's absolute reflectivity per pixel for 122 wavelengths by modeling the vertical distribution of the lower atmosphere haze and tropospheric methane. Analysis of these data suggests that Titan's haze concentration in the lower atmosphere varies in strength with latitude. We find Titan's tropospheric methane profile to be fairly consistent with latitude and longitude, and we find evidence for local areas of a CH 4–N 2 binary saturation in Titan's troposphere. Our results suggest that a methane and haze profile at one location on Titan would not be representative of global conditions.