Wave constraints for Titan’s Jingpo Lacus and Kraken Mare from VIMS specular reflection lightcurves |
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Authors: | Jason W Barnes Jason M Soderblom Laurence A Soderblom Ralf Jaumann Sebastien Rodriguez Bonnie J Buratti Roger N Clark |
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Institution: | a Department of Physics, University of Idaho, Moscow, ID 83844-0903, United States b Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, United States c United States Geological Survey, Flagstaff, AZ 86001, United States d DLR, Institute of Planetary Research, Rutherfordstrasse 2, D-12489 Berlin, Germany e Laboratoire de Planétologie et Géodynamique, CNRS UMR6112, Université de Nantes, France f Laboratoire AIM, Centre d’ètude de Saclay, DAPNIA/Sap, Centre de l’Orme des M erisiers, bât. 709, 91191 Gif/Yvette Cedex, France g Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, United States h United States Geological Survey, Denver, CO 80225, United States i Department of Astronomy, Cornell University, Ithaca, NY 14853, United States |
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Abstract: | Stephan et al. (Stephan, K. et al. 2010]. Geophys. Res. Lett. 37, 7104-+.) first saw the glint of sunlight specularly reflected off of Titan’s lakes. We develop a quantitative model for analyzing the photometric lightcurve generated during a flyby in which the specularly reflected light flux depends on the fraction of the solar specular footprint that is covered by liquid. We allow for surface waves that spread out the geographic specular intensity distribution. Applying the model to the VIMS T58 observations shows that the waves on Jingpo Lacus must have slopes of no greater than 0.15°, two orders of magnitude flatter than waves on Earth’s oceans. Combining the model with theoretical estimates of the intensity of the specular reflection allows a tighter constraint on the waves: ?0.05°. Residual specular signal while the specular point lies on land implies that either the land is wetted, the wave slope distribution is non-Gaussian, or that 5% of the land off the southwest edge of Jingpo Lacus is covered in puddles. Another specular sequence off of Kraken Mare acquired during Cassini’s T59 flyby shows rapid flux changes that the static model cannot reproduce. Points just 1 min apart vary in flux by more than a factor of two. The present dataset does not uniquely determine the mechanism causing these rapid changes. We suggest that changing wind conditions, kilometer-wavelength waves, or moving clouds could account for the variability. Future specular observations should be designed with a fast cadence, at least 6 points per minute, in order to differentiate between these hypotheses. Such new data will further constrain the nature of Titan’s lakes and their interactions with Titan’s atmosphere. |
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Keywords: | Titan Photometry Satellites surfaces |
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