High resolution spectroscopy of Pluto's atmosphere: detection of the 2.3 $\mu$m CH${}_4$ bands and evidence for carbon monoxide

Abstract

The goal is to determine the composition of Pluto's atmosphere and to constrain the nature of surface-atmosphere interactions. We perform high--resolution spectroscopic observations in the 2.33--2.36 $\mu$m range, using CRIRES at the VLT. We obtain (i) the first detection of gaseous methane in this spectral range, through lines of the ${\nu }_3$ + ${\nu }_4$ and ${\nu }_1$ + ${\nu }_4$ bands (ii) strong evidence (6-$\sigma$ confidence) for gaseous CO in Pluto. For an isothermal atmosphere at 90 K, the CH${}_4$ and CO column densities are 0.75 and 0.07 cm-am, within factors of 2 and 3, respectively. Using a physically--based thermal structure model of Pluto's atmosphere also satisfying constraints from stellar occultations, we infer CH${}_4$ and CO mixing ratios q${}_{C{H}_4}$= 0.6${}_{-0.3}^{+0.6}$% (consistent with results from the 1.66 $\mu$m range) and q${}_{CO}$ = 0.5${}_{-0.25}^{+1}$$\times 10^{-3}$. The CO atmospheric abundance is consistent with its surface abundance. As for Triton, it is probably controlled by a thin, CO-rich, detailed balancing layer resulting from seasonal transport and/or atmospheric escape.

Astronomy and Astrophysics Letters, in press

References in corpus (3)

• Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations
• Detection of CO in Triton's atmosphere and the nature of surface-atmosphere interactions
• Near-Infrared Spectral Monitoring of Triton with IRTF/SpeX II: Spatial Distribution and Evolution of Ices

Cited by in corpus (19)

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• Constraints on the Microphysics of Pluto's Photochemical Haze from New Horizons Observations
• Near-Infrared Spectral Monitoring of Pluto's Ices: Spatial Distribution and Secular Evolution
• Carbon Monoxide Affecting Planetary Atmospheric Chemistry
• The composition of the protosolar disk and the formation conditions for comets
• The CH4 cycles on Pluto over seasonal and astronomical timescales
• The Effect of Carbon Monoxide on Planetary Haze Formation
• Exploring the spatial, temporal, and vertical distribution of methane in Pluto's atmosphere
• Volatile transport on inhomogeneous surfaces: I. Analytic expressions, with application to Pluto's day
• A 3D general circulation model for Pluto and Triton with fixed volatile abundance and simplified surface forcing
• Nitrogen Atmospheres of the Icy Bodies in the Solar System
• Volatile transport modeling on Triton with new observational constraints
• Pluto's Ultraviolet Spectrum, Surface Reflectance, and Airglow Emissions
• An atmospheric general circulation model for Pluto with predictions for New Horizons temperature profiles
• The first detection of an atmosphere on a trans-Neptunian object beyond Pluto
• Pluto's atmosphere observations with ALMA: spatially-resolved maps of CO and HCN emission and first detection of HNC