Deborah & William Hillyard
Deborah & William Hillyard
Deborah & William Hillyard
Deborah & William Hillyard
Deborah & William Hillyard
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Solar System -
Jupiter's Moons
Io
Io is the innermost of Jupiter's four Galilean moons, the others being Europa, Ganymede and Callisto. It has a diameter of 3,642 kilometers (2,263 miles), and orbits at a distance of 421,700 km (262,000 miles) from Jupiter. Interestingly, Io's orbit is in a 2:1 resonance with Europa (two orbits for every one of Europa) and a 4:1 resonance with Ganymede (four orbits for every one of Ganymede). It orbits once every ~42.5 hours, and rotates synchronously keeping the same hemisphere facing Jupiter.
Io is said to be the most geologically active object in our Solar System having more than 400 known active volcanoes producing huge sulfurous plumes that rise to over 500 km (310 miles) in Io's weak gravity. The lava flows produced are similarly large, many reaching more than 500 km (310 miles). There are large number of mountains, up to about 150, some of which exceed the height of mount Everest reaching 18 km (11 miles) high. This geological activity is largely the result of tidal heating caused by being pulled around by Jupiter and the resonances with the other Galilean moons. The constant renewing of the surface has also obliterated traces of craters left by meteor bombardment. There are large number of mountains, up to about 150, some of which exceed the height of mount Everest reaching 18 km (11 miles) high. The mountains appear to be formed by compression in Io's lithosphere.
Io has a molten iron core, making up about 20% of its mass. The core also contains unknown proportions of sulfur and nickel. This core is surrounded by a rocky layer, that may be partly molten, with a rocky surface covered in sulfur and sulfur dioxide frost.
Io is said to be the most geologically active object in our Solar System having more than 400 known active volcanoes producing huge sulfurous plumes that rise to over 500 km (310 miles) in Io's weak gravity. The lava flows produced are similarly large, many reaching more than 500 km (310 miles). There are large number of mountains, up to about 150, some of which exceed the height of mount Everest reaching 18 km (11 miles) high. This geological activity is largely the result of tidal heating caused by being pulled around by Jupiter and the resonances with the other Galilean moons. The constant renewing of the surface has also obliterated traces of craters left by meteor bombardment. There are large number of mountains, up to about 150, some of which exceed the height of mount Everest reaching 18 km (11 miles) high. The mountains appear to be formed by compression in Io's lithosphere.
Io has a molten iron core, making up about 20% of its mass. The core also contains unknown proportions of sulfur and nickel. This core is surrounded by a rocky layer, that may be partly molten, with a rocky surface covered in sulfur and sulfur dioxide frost.
Taken July 3rd, 1999 by the Galileo probe. The very bright areas are reflections of sunlight. The erupting volcano Prometheus is the dark spot just left of center. The lighter colored plains are coated in sulfur dioxide frost from volcanism, while the yellower areas are encrusted with a higher proportion of sulfur. The image is close to true color.
The Galileo probe took this photograph on September 19, 1997 from a distance of more than 500,000 kilometers (310,000 miles). The image has been color enhanced, and shows sulfur dioxide frost in white and grey with sulfur in yellows and browns. The red areas and the dark spots indicate recent volcanic eruptions. The almost circular red ring surrounds Pele, and the dark spot breaking the red ring is the volcano Pillan Patera. This produced a 120 kilometer (75 mile) high plume in an earlier eruption.
Schematic of the interior of Io showing:
This photograph is a composite of images taken in September and November 1996 by Galileo. The color variations have been enhanced to emphasize color variations. The full sized version is available on the NASA website.
The central iron or iron sulfide core in gray,
the rocky mantle around the core in orange/yellow,
the rocky outer crust in brown,
the rocky mantle around the core in orange/yellow,
the rocky outer crust in brown,
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Inner Moons • Io • Europa • Ganymede • Callisto • Himalia Group • Carme Group • Ananke Group • Pasiphae Group • Miscellaneous
Jupiter's moons are grouped as follows. Select to see details of the moon or the group of moons: