Io (moon)

Io ({{IPA2|?a?o?}}, eye'-oe, Greek Ιώ) is the innermost of the four Galilean moons of Jupiter. It is named after the Greek mythological figure Io, one of the many lovers of Zeus (who is also known as Jupiter in the Roman mythology).

Volcanism

Io is most noteworthy for its volcanic nature; it is the most volcanically active body in the Solar System. Similarly to volcanoes on Earth, Ionian volcanoes emit sulfur and sulfur dioxide. Originally it was thought that many lava flows consisted of sulfurous substances. However, nowadays it is thought that many of them are molten silicate rock like on the Earth.

Related Topics:
Solar System - Volcano - Earth - Sulfur - Sulfur dioxide - Lava - Substances - Silicate

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The energy for this activity probably derives from tidal interactions among Io, Jupiter, and two other moons of Jupiter, Europa and Ganymede. The three moons are locked into Laplace-resonant orbits such that Io orbits twice for each orbit of Europa, which in turn orbits twice for each orbit of Ganymede; furthermore, Io always keeps the same face towards Jupiter. The gravitational interaction of Europa, Ganymede and Jupiter cause Io to "stretch" and "bend" by as much as 100 meters, a process which generates heat through internal friction.

Related Topics:
Tidal - Europa - Ganymede - Laplace-resonant orbits

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Some of Io's volcanic plumes have been measured rising over 300 km above the surface before falling back, with material ejected from the surface at approximately one kilometre per second. The volcanic eruptions change rapidly; in just four months between the arrivals of Voyager 1 and Voyager 2 some eruptions stopped and others began. The deposits surrounding the vents also changed visibly during this time.

Related Topics:
Voyager 1 - Voyager 2

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Another source of energy is that Io cuts across Jupiter's magnetic field lines, generating an electric current. Though not a large source of energy compared to the tidal heating, this current may carry more than 1,000 gigawatts with a potential of 400 kilovolts. It also strips ionized atoms from Io at the rate of a thousand kilograms per second. Due to the rapid rotation of Jupiter's magnetic field, these particles are swept along the orbit in front of Io where they form a torus of intense radiation around Jupiter that glows brightly in the ultraviolet. Particles escaping from this torus are partially responsible for Jupiter's unusually large magnetosphere, their outward pressure inflating it from within. Recent data from the Galileo orbiter indicate that Io might have its own magnetic field.

Related Topics:
Magnetic field - Electric current - Watt - Volt - Ionized atoms - Ultraviolet - Magnetosphere - Galileo

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The location of Io with respect to the Earth and Jupiter has a strong influence on the Jovian radio emissions as seen from the earth: When Io is visible, radio signals from Jupiter increase considerably.

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In February 2001, the largest recorded volcanic eruptions in the solar system occurred on Io http://www2.keck.hawaii.edu/news/archive/eruption/.

Related Topics:
2001 - Solar system

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