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An analysis of Pluto occultation light curves using an atmospheric radiative-conductive model |
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| Authors: | Angela M Zalucha Amanda AS Gulbis Xun Zhu JL Elliot |
| Institution: | a Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA b Southern African Large Telescope and South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 Cape Town, South Africa c Applied Physics Laboratory, The Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20723, USA d Department of Earth and Planetary Sciences, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA e Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA f Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA g Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA |
| Abstract: | We use a radiative-conductive model to least-squares fit Pluto stellar occultation light curve data. This model predicts atmospheric temperature based on surface temperature, surface pressure, surface radius, and CH4 and CO mixing ratios, from which model light curves are to be calculated. The model improves upon previous techniques for deriving Pluto’s atmospheric thermal structure from stellar occultation light curves by calculating temperature (as a function of height) caused by heating and cooling by species in Pluto’s atmosphere, instead of a general assumption that temperature follows a power law with height or some other idealized function. We are able to fit for model surface radius, surface pressure, and CH4 mixing ratio with one of the 2006 datasets and for surface pressure and CH4 mixing ratio for other datasets from the years 1988, 2002, 2006, and 2008. It was not possible to fit for CO mixing ratio and surface temperature because the light curves are not sensitive to these parameters. We determine that the model surface radius, under the assumption of a stratosphere only (i.e. no troposphere) model in radiative-conductive balance, is  . The CH4 mixing ratio results are more scattered with time and are in the range of 1.8-9.4 × 10−3. The surface pressure results show an increasing trend from 1988 to 2002, although it is not as dramatic as the factor of 2 from previous studies. |
| Keywords: | Occultations Pluto Atmosphere Atmospheres Composition |
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