EGU23-8541
https://doi.org/10.5194/egusphere-egu23-8541
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Callisto’s atmosphere: First evidence for H2, and the implications this has for Europa’s and Ganymede’s atmosphere

Shane Carberry Mogan1, Orenthal J. Tucker2, Robert E. Johnson3,4, Lorenz Roth5, Juan Alday6, Audrey Vorburger7, Peter Wurz7, Andre Galli7, H. Todd Smith7, Apurva V. Oza7,9, Lucas Liuzzo1, and Andrew R. Poppe1
Shane Carberry Mogan et al.
  • 1Space Sciences Laboratory, University of California, Berkeley, Berkeley, USA
  • 2NASA Goddard Space Flight Center, Greenbelt, USA
  • 3University of Virginia, Charlottesville, USA
  • 4New York University, New York, USA
  • 5KTH Royal Institute of Technology, Stockholm, Sweden
  • 6Open University, Milton Keynes, England
  • 7University of Bern, Bern, Switzerland
  • 9Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA

We explore the parameter space for the contribution to Callisto's H corona observed by the Hubble Space Telescope from sublimated H2O and radiolytically produced H2 using the Direct Simulation Monte Carlo (DSMC) method. The spatial morphology of this corona produced via photo- and magnetospheric electron impact-induced dissociation is described by tracking the motion of and simulating collisions between the hot H atoms and thermal molecules including a near-surface O2 component. Our results presented indicate that sublimated H2O produced from the surface ice, whether assumed to be intimately mixed with or distinctly segregated from the dark non-ice or ice-poor regolith, cannot explain the observed structure of the H corona. On the other hand, a global H2 component can reproduce the observation, and is also capable of producing the enhanced electron densities observed at high altitudes by Galileo's plasma-wave instrument, providing the first evidence of H2 in Callisto's atmosphere. Finally, we discuss the implications of these results, in particular how they compare to Europa and Ganymede.

How to cite: Carberry Mogan, S., Tucker, O. J., Johnson, R. E., Roth, L., Alday, J., Vorburger, A., Wurz, P., Galli, A., Smith, H. T., Oza, A. V., Liuzzo, L., and Poppe, A. R.: Callisto’s atmosphere: First evidence for H2, and the implications this has for Europa’s and Ganymede’s atmosphere, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8541, https://doi.org/10.5194/egusphere-egu23-8541, 2023.