Detection of CO in Triton's atmosphere and the nature of surface-atmosphere interactions

Abstract

Triton possesses a thin atmosphere, primarily composed of nitrogen, sustained by the sublimation of surface ices. The goal is to determine the composition of Triton's atmosphere and to constrain the nature of surface-atmosphere interactions. We perform high-resolution spectroscopic observations in the 2.32-2.37 $\mu$m range, using CRIRES at the VLT. From this first spectroscopic detection of Triton's atmosphere in the infrared, we report (i) the first observation of gaseous methane since its discovery in the ultraviolet by Voyager in 1989 and (ii) the first ever detection of gaseous CO in the satellite. The CO atmospheric abundance is remarkably similar to its surface abundance, and appears to be controlled by a thin, CO-enriched, surface veneer resulting from seasonal transport and/or atmospheric escape. The CH${}_4$ partial pressure is several times larger than inferred from Voyager. This confirms that Triton's atmosphere is seasonally variable and is best interpreted by the warming of CH${}_4$-rich icy grains as Triton passed southern summer solstice in 2000. The presence of CO in Triton's atmosphere also affects its temperature, photochemistry and ionospheric composition. An improved upper limit on CO in Pluto's atmosphere is also reported.

11 pages, including 4 figures and 2 on-line figures Astronomy and Astrophysics, in press (accepted March 13, 2010)

References in corpus (2)

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

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• Constraints on the structure and seasonal variations of Triton's atmosphere from the 5 October 2017 stellar occultation and previous observations
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• Triton Haze Analogues: the Role of Carbon Monoxide in Haze Formation
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• Volatile transport modeling on Triton with new observational constraints
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• Surface Volatile Composition as Evidence for Hydrothermal Processes Lasting Longer in Triton's Interior than Pluto's
• New constraints on Triton's atmosphere from the 6 October 2022 stellar occultation
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