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Detailed Changes in Pluto’s Atmosphere from Recent Occultations

Presentation #308.03 in the session Pluto System (Oral Presentation)

Published onOct 23, 2023
Detailed Changes in Pluto’s Atmosphere from Recent Occultations

When Pluto occults a star, the resulting lightcurves allow retrievals of Pluto’s temperature, pressure and density profiles and, if lightcurves are obtained in two wavelengths, retrievals of haze optical depths. Results from 1989 through 2022 – including the 2015 New Horizons Radio Occultation Experiment profiles [1] and UV solar occultation results [2] – let us track Pluto’s changing surface pressure and its rapidly varying haze opacity. In 2018 and 2022, we observed multiple lightcurves near the central chord. We report on evidence from those chords of Pluto’s long-expected atmospheric freeze-out. We also report on year-by-year changes in Pluto’s haze opacities – the 2007, 2018 and 2022 data sets include dramatic central flashes, which are very sensitive to haze opacity. We discuss other implications of occultation results, from constraints on Pluto’s surface thermal inertia (from the time-evolution of changing surface pressures) to atmospheric escape (due to changes in haze optical depths, which normally cool the upper atmosphere [3]). We also examine how Pluto’s atmospheric figure and near-surface temperature structure affect the morphology of central flashes.

[1] https://doi.org/10.1016/j.icarus.2017.02.031

[2] https://doi.org/10.1016/j.icarus.2017.09.006

[3] https://doi.org/10.1038/nature24465

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