Pluto's Minimum Pressure in the Current Season from a Thermophysical Model
Abstract
A model balancing solar insolation, substrate thermal inertia, and thermal emission (Young 2017, Icarus 284 433-476) is used to determine the volatile temperature and pressure at Pluto's surface over the course of its year. Our initial model assumes for simplicity that Sputnik Planitia, with borders defined by the New Horizons mapping of geologic units (White et al. 2017, Icarus 287 261-286), is the only volatile-covered region, and that the volatiles have spatially uniform albedo and emissivity. The reasoning for this volatile distribution is in part motivated by the GCM results of Bertrand and Forget (2016, Nature 540 86-89), which show all volatiles confined to a Sputnik Planitia-like basin after 10,000 Earth years. Thermal parameter values were varied over many runs in order to produce pressures consistent with existing stellar occultation measurements as well as the New Horizons measurement of 11 µbar in 2015. This work is motivated by a desire to learn the minimum pressure experienced at Pluto's surface. This can help determine if the atmosphere ever becomes non-global (Spencer et al. 1997, in Pluto and Charon p 435), and if the atmosphere ever becomes transparent to Lyman-α or EUV radiation. Transparency to radiation could help explain the puzzling lack of settled-out haze particles on the surface, by providing a method of disrupting haze production, which may be needed to explain Pluto's heterogeneity (Cheng et al. 2017, Icarus 290 112-133; Grundy et al. 2018, Icarus 314 232-245). Since our methodology is completely distinct from Bertrand and Forget (2016), the independent results can be used as means of checking both models. This work was supported by NASA ROSES/SSW grant NNX15AH35G.
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5050204J