Energetic Ion and Electron Irradiation of the Icy Galilean Satellites
By J. Cooper, Robert E. Johnson, B. Mauk, H. Garrett, N. Gehrels. 2001
431 citations recorded by the source corpus.
Abstract Galileo Orbiter measurements of energetic ions (20 keV to 100 MeV) and electrons (20–700 keV) in Jupiter's magnetosphere are used, in conjunction with the JPL electron model ( 6 years, whereas micrometer depths on Europa are fully processed in ∼10 years. Most observations of surface composition are limited to optical depths of ∼1 mm, which are in direct contact with the space environment. Incident flux modeling includes Stormer deflection by the Ganymede dipole magnetic field, likely variable over that satellite's irradiation history. Delivered energy flux of ∼8×10 10 keV (cm 2 -s) −1 at Europa is comparable to total internal heat flux in the same units from tidal and radiogenic sources, while exceeding that for solar UV energies (>6 eV) relevant to ice chemistry. Particle energy fluxes to Ganymede's equator and Callisto are similar at ∼2–3×10 8 keV (cm 2 -s) −1 with 5×10 9 at Ganymede's polar cap, the latter being comparable to radiogenic energy input. Rates of change in optical reflectance and molecular composition on Europa, and on Ganymede's polar cap, are strongly driven by energy from irradiation, even in relatively young regions. Irradiation of nonice materials can produce SO 2 and CO 2 , detected on Callisto and Europa, and simple to complex hydrocarbons. Iogenic neutral atoms and meteoroids deliver negligible energy ∼10 4–5 keV (cm 2 -s) −1 but impacts of the latter are important for burial or removal of irradiation products. Downward transport of radiation produced oxidants and hydrocarbons could deliver significant chemical energy into the satellite interiors for astrobiological evolution in putative sub-surface oceans.
Subfields: Astronomy and Astrophysics, Ecology
View Paper: https://www.semanticscholar.org/paper/34a8dc87f4790965532ae4f58622f9ef5e75b61e
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Citations in the corpus
- IR Detection of H2O2 at 80 K in Ion-Irradiated Laboratory Ices Relevant to Europa (2000, background): “The estimated value of the incident energy flux (Cooper et al. 2000) is included in Table I for each satellite.”
- Magnetospheric ion sputtering and water ice grain size at Europa (2013, methodology): “We chose a charge state of 2þ for the oxygen and 3þ sulfur ions, following Cooper et al. (2001) (and references therein).”
- Geophysical controls of chemical disequilibria in Europa (2016, background): “Europa, Ganymede, and Callisto receive averages of 125, 6, and 0.6 mW m−2 [Cooper et al., 2001; Johnson, 2004].”
- X-rays from solar system objects (2007, background): “X-ray emission from Callisto seems likely at levels not too far below the CXO sensitivity limit, since the magnetospheric heavy ion fluxes (Cooper et al., 2001) are an order of magnitude lower than at Ganymede and Europa, respectively.”
- Radiation effects on the surfaces of the Galilean satellites (2004, methodology): “Implantation is not a likely source unless there is a relatively high abundance of carbon ions at energies below 10 keV, where Ganymede’s magnetic shielding is less effective (Cooper et al. 2001).”
- Ice structures, patterns, and processes: A view across the icefields (2012, background): “Comparison with laboratory spectra indicates a surface concentration of about 0.13%, by number of molecules, relative to water ice. Europa is immersed in a highly energetic plasma environment originating in Jupiter’s magnetosphere (Cooper et al., 2001).”
- Composition and stability of salts on the surface of Europa and their oceanic origin (2001, methodology): “In addition, we have to take into account fractionation, redistribution, and radiolytic synthesis of surface material caused by magnetospheric bombardment, sputtering, and implantation [e.g., Cooper et al., 2001].”