Pluto Photochemical Models for the New Horizons Flyby

Abstract:

During the New Horizons flyby of the Pluto system on July 14, 2015 a number of observations will be made to determine the structure, composition, and variability of Pluto’s atmosphere. A key observation of this type is the Alice solar occultation, which will measure the full disk ultraviolet (52-187 nm) spectral flux from the Sun through ingress and egress behind Pluto, about one hour after closest approach. This observation will be used to determine the temperature and vertical density profiles of N₂, CH₄, and various minor species above two regions of very different surface albedo. Nearly simultaneous Earth ingress and egress occultations observed in X-band uplink will provide profiles of temperature and pressure in Pluto’s lower atmosphere, and electron densities in the ionosphere. Wave structures in both the solar and radio occultation data will provide constraints on atmospheric dynamics. In order to interpret and understand these data sets, we have modified a 1-D Titan photochemical model to Pluto, for the epoch of the New Horizons flyby. The model uses a similar, but updated reaction list to that of Krasnopolsky and Cruikshank [1999] and Wong et al. [2014], and adopts the results of Zhu et al. [2014] for the background atmosphere. We present here initial results for several assumed eddy diffusion profiles.

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Wong, M. L., Y. L. Yung, and G. R. Gladstone, Icarus, in press, 2014.

Zhu, X., D F. Strobel, and J. T. Erwin, Icarus, 228, 301, 2014.