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Atmosphere of Callisto

Liang, Mao-Chang and Lane, Benjamin F. and Pappalardo, Robert T. and Allen, Mark and Yung, Yuk L. (2005) Atmosphere of Callisto. Journal of Geophysical Research E, 110 (E2). Art. No. E02003. ISSN 0148-0227. doi:10.1029/2004JE002322.

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During the Galileo flybys of Callisto in 1999, a CO_2 atmosphere and an ionosphere were detected. Using the Caltech/Jet Propulsion Laboratory one-dimensional KINETICS model, we have successfully simulated the observed electron density within a factor of 2, while satisfying the observational constraints on carbon and oxygen atoms. We conclude that photoionization of CO_2 alone is insufficient to produce the observed electron density. An atmosphere 20–100 times denser than the CO_2 atmosphere must be introduced, as suggested by Kliore et al. (2002). We show that an O_2-rich atmosphere is highly probable. However, the atomic oxygen produced from O_2 photodissociation is 2 orders of magnitude greater than the upper limit given by Strobel et al. (2002). The introduction of reactive hydrogen chemistry assuming a surface abundance of H_2O of ∼2 × 10^9 cm^(−3) (4 × 10^(−8) mbar) is required to reduce the excess atomic O abundance. The calculated atomic O column density is >5 × 10^(12) cm^(−2), which is about the observed upper limit, suggesting we should be able to detect O in the atmosphere of Callisto.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Liang, Mao-Chang0000-0002-5294-9344
Yung, Yuk L.0000-0002-4263-2562
Additional Information:© 2005 The American Geophysical Union. Received 11 July 2004; Revised 17 October 2004; Accepted 1 December 2004; Published 8 February 2005. We thank M. Gerstell, R. L. Shia, D. J. Stevenson, and D. F. Strobel for valuable discussions. This research was supported in part by NASA grant NAG5-6263 to the California Institute of Technology. B.F.L. gratefully acknowledges the support of a Pappalardo Fellowship in Physics of MIT.
Funding AgencyGrant Number
Pappalardo Fellowship in PhysicsUNSPECIFIED
Issue or Number:E2
Record Number:CaltechAUTHORS:20140825-144257305
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Official Citation:Liang, M.-C., Lane, B. F., Pappalardo, R. T., Allen, M., & Yung, Y. L. (2005). Atmosphere of Callisto. Journal of Geophysical Research: Planets, 110(E2), E02003. doi: 10.1029/2004je002322
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48861
Deposited By: Joanne McCole
Deposited On:25 Aug 2014 22:17
Last Modified:10 Nov 2021 18:37

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