Titan's bright spots: Multiband spectroscopic measurement of surface diversity and hazes

摘要

Spatially resolved near-infrared spectra of Titan, which simultaneously cover two CH4 absorption bands (from 1.45 to 2.45 μm), have been obtained using the SINFONI integral-field spectrometer with adaptive optics at the Very Large Telescope (VLT) of the European Southern Observatory. We observe the enhancement in 2 μm surface albedo of the “5 μm bright spot” at 80°W and 24°S, and find an analogously bright region at 2 μm near 88°W and 6°S. Surface albedos are recovered at ～60 mas (375 km) resolution in both 1.5 and 2.0 μm windows using a two-stream, plane-parallel, radiative transfer model to fit the observed spectra. The surface albedos near the center of the disk range from 8 to 15% at 1.5 μm and are generally ～2% lower at 2.0 μm. Vertical (altitude) profiles of aerosol extinction that are consistent with the Huygens/DISR measurements are used to model these observations, and we retrieve latitudinal trends in both stratospheric and tropospheric aerosol extinction. On 28 February 2005 UT, the stratospheric aerosol extinction is measured to increase linearly at a rate of 0.65 ± 0.05% per degree latitude from 40°S to 60°N. Meanwhile, the tropospheric haze near the south pole is confined to southern latitudes above 40°S and is enhanced in extinction by a factor of ～1.7 relative to the extinction measured at 10°S, the latitude where the Huygens probe landed.