Astrophysics (Index)About


(Jupiter I)
(well-known Jupiter moon)

Io (Jupiter I) is the nearest to Jupiter of the first four of its moons discovered, and is the fourth moon outward from the planet according to current knowledge. Its radius is 1821 km (a bit over a quarter or 2/7 of Earth's), its mass is 8.9×1022kg (about 1/66 of Earth's), with a mean density about three and a half times that of water (a bit over half or 7/11 Earth's). Io's orbital period is 1.75 days and it is tidally locked. Its orbit is in sync with Ganymede (1/4) and Europa (1/2). Of interest are the "real" volcanos on the surface, i.e., with temperatures above 1000 K rather than cryovolcanos like those found on other solar system moons. Flyby observations of Io have been made by the Pioneer, Voyager, and Galileo missions.

The Io torus (or Io plasma torus) is a gas torus, which is a torus-shaped cloud surrounding a planet, typically associated with a moon. In Io's case, it is plasma from its volcanic eruptions shaped by Jupiter's magnetic field.

Further reading:
/Lookback Years

Referenced by pages:
magnetic field