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Another look at Polaznik Macula: Views from Multiple Angles to Separate HazeDistribution from Surface Albedo

Presentation #411.04 in the session “Cloudy and Hazy on Titan”.

Published onOct 26, 2020
Another look at Polaznik Macula: Views from Multiple Angles to Separate HazeDistribution from Surface Albedo

We use Cassini-Huygens Visual and Infrared Mapping Spectrometer (VIMS) spectra taken from flybys T53 through T76 to fit for haze and methane distribution around the region of Polaznik Macula on Titan. This region was selected for several reasons: it is a very dark surface and thus the surface contribution to the spectra is minimized; the region was previously analyzed, allowing validation of our findings; and on T66, spectra of this region were obtained from multiple viewing geometries (emission, incidence, and phase angles), allowing us to distinguish haze scattering from surface albedo effects. To fit for haze, methane, and surface albedo, we use PyDISORT, a radiative transfer code developed to model Titan’s atmosphere (Ádámkovics et al. 2016). Using PyDISORT, we can generate sensitivity studies for haze, methane, and surface albedo, and isolate these parameters. To speed the fitting process, we generate spectra over a grid using PyDISORT, and use an interpolation function and fitting tool to find the best-fit methane, haze, and surface albedo parameters. Having multiple angles of emission allows us to constrain the vertical haze distribution, and in general, we are finding that an increased haze abundance in the upper atmosphere and a decreased haze abundance in the lower atmosphere is providing a better fit to VIMS spectra. We report on the surface albedo over a small region of Polaznik Macula in the methane windows at 1.6, 2.0, 2.7-2.8 and 4.9 µm, and compare our findings to the findings to Vixie et al. (2012) and to the ISS map of the same region. We are looking at variations over time from flybys T53 (occurring on April 20, 2009) to T76 (occurring May 8, 2011), a time frame spanning a storm event on Titan, in an attempt to look for possible effects of seasonal storms on surface variability, and ideally, methane abundance.


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