A Tenuous Carbon Dioxide Atmosphere on Jupiter's Moon Callisto
Abstract
An off-limb scan of Callisto was conducted by the Galileo near-infrared mapping spectrometer to search for a carbon dioxide atmosphere. Airglow in the carbon dioxide ν3 band was observed up to 100 kilometers above the surface and indicates the presence of a tenuous carbon dioxide atmosphere with surface pressure of 7.5 × 10−12 bar and a temperature of about 150 kelvin, close to the surface temperature. A lifetime on the order of 4 years is suggested, based on photoionization and magnetospheric sweeping. Either the atmosphere is transient and was formed recently or some process is currently supplying carbon dioxide to the atmosphere.
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I thank M. Segura for implementing the observing sequence, B. Mehlman for data processing, and F. Fanale for pointing out the possibility of water sublimation limiting CO2 effusion. The work described herein was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
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Published In
Science
Volume 283 | Issue 5403
5 February 1999
5 February 1999
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Received: 3 November 1998
Accepted: 23 December 1998
Published in print: 5 February 1999
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