The Space Environment of Io and Europa

The Galilean moons play major roles in the giant magnetosphere of Jupiter. At the same time, the magnetospheric particles and fields affect the moons. The impact of magnetospheric ions on the moons' atmospheres supplies clouds of escaping neutral atoms that populate a substantial fraction of their orbits. At the same time, ionization of atoms in the neutral cloud is the primary source of magnetospheric plasma. The stability of this feedback loop depends on the plasma/moon-atmosphere interaction. The purpose of this review is to describe the physical processes that shape the space environment around the two innermost Galilean moons-Io and Europa-and to show their impact from the planet Jupiter out into interplanetary space. Key Points Io and Europa substantially impact the Jovian magnetosphere while interactions of plasma with moons affects their surfaces and atmospheres Ten components are described, including neutrals, thermal plasma, and energetic particles, spanning from Jupiter to interplanetary medium Current understanding of the systems and processes are reviewed with a summary of outstanding questions