Skip to main content
Dryad logo

Data underlying the publication: Callisto's atmosphere: First evidence for H2 and constraints on H2O


Carberry Mogan, Shane (2022), Data underlying the publication: Callisto's atmosphere: First evidence for H2 and constraints on H2O, Dryad, Dataset,


We explore the parameter space for the contribution to Callisto's H corona observed by the Hubble Space Telescope (Roth et al. 2017a) 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 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 consistent with enhanced electron densities observed at high altitudes by Galileo's plasma-wave instrument (Gurnett et al. 1997, 2000), providing the first evidence of H2 in Callisto's atmosphere. The range of H2 surface densities explored, under a variety of conditions, that are consistent with these observations is ∼(0.4-1)×108 cm-3. The simulated H2 escape rates and estimated lifetimes suggest that Callisto has a neutral H2 torus. We also place a rough upper limit on the peak H2O number density (<∼108 cm-3), column density (<∼1015 cm-2), and sublimation flux (<∼1012 cm-2 s-1), all of which are 1-2 orders of magnitude less than that assumed in previous models. Finally, we discuss the implications of these results, as well as how they compare to Europa and Ganymede.

Usage Notes

The figures were produced using Python, but any software that is able to read .txt files should suffice.


NASA Goddard Space Flight Center