A Tenuous Carbon Dioxide Atmosphere on Jupiter's Moon Callisto
Robert W. Carlson
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
3 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.
Jet Propulsion Laboratory, California Institute of Technology,
Mail Stop 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
E-mail: rcarlson{at}lively.jpl.nasa.gov