Cut-away schematic of Jupiter's space environment showing magnetically trapped radiation ions (in red), the neutral gas torus of the volcanic moon Io (green) and the newly discovered neutral gas torus of the moon Europa (blue). The white lines represent magnetic field lines. Energetic neutral atoms (ENAs) are emitted from the Europa torus regions because of the interaction between the trapped ions and the neutral gases.
The Cassini Magnetospheric Imaging Instrument imaged those ENAs during flyby of Jupiter in early 2001. ENAs also come from Jupiter when radiation ions impinge onto Jupiter's upper atmosphere.
Credit: NASA/Jet Propulsion Lab/Johns Hopkins University Applied Physics Laboratory
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