Observations made during the New Horizons flyby provide a detailed snapshot of the current state of Pluto's atmosphere. While the lower atmosphere (at altitudes <200 km) is consistent with ground-based stellar occultations, the upper atmosphere is much colder and more compact than indicated by pre-encounter models. Molecular nitrogen (N 2 ) dominates the atmosphere (at altitudes <1800 km or so), while methane (CH 4 ), acetylene (C 2 H 2 ), ethylene (C 2 H 4 ), and ethane (C 2 H 6 ) are abundant minor species, and likely feed the production of an extensive haze which encompasses Pluto. The cold upper atmosphere shuts off the anticipated enhanced-Jeans, hydrodynamic-like escape of Pluto's atmosphere to space. It is unclear whether the current state of Pluto's atmosphere is representative of its average state-over seasonal or geologic time scales.

No abstract

No abstract

Abstract.Previous observations of atmospheric oscillations with zonal wave number 1 have consistently located waves of periods between 5 and 7 days. This study presents a global and seasonal analysis of the 6.5-day wave in High Resolution Doppler Imager daytime mesosphere and lower thermosphere horizontal winds, temperatures, and nighttime atomic oxygen at 95 km. The horizontal structures of all these atmospheric variables are similar to the gravest symmetric wave number 1 Rossby wave, i.e., the (1,1) mode. The seasonal and spatial analysis displays possible modification by the zonal mean wind. Finally, the observed vertical structures of the 6.5-day wave indicate that it is an internal Rossby wave, not an external or Lamb wave.

No abstract