A Jovian Satellite: The Tormented Fireball of our Solar System!

By: Kimberly Miller

Historical Findings

• The satellite Io was discovered on January 7th, 1610 by Astronomer and Scientist Galileo Galilei using a homemade telescope.

• Appearing as three stars linearly transecting Jupiter, intrigue captivated the astronomer the following night, as these stars seemed to shift in the wrong direction.

• This allowed for the discovery of a forth star (later known as Ganymede) and the notion that, after a week of observation, these were indeed planetary bodies that remained in the orbiting realm of Jupiter.

• This discovery was historical in providing evidence that sustained the Copernican system theories and how the Earth is not the center of the Universe.

• Io was numerically labeled: I, according to the Medicean planet system (Europa II, Ganymede III, and Callisto IV).

Died: January 8th, 1642

Born: February 15th, 1564

• Simon Marius is also given credit for discovering the satellites within the same time frame and was in fact the provider of the names we are familiar with presently (Io, Callisto, Europa, and Ganymede).

• Io was named, based on a suggestion from Johannes Kepler, after the maiden daughter of the River (according to Roman mythology), having been clandestinely courted by the Roman God, Jupiter.

Mass (kg) 8.94e+22  Mass (Earth = 1) 1.4960e-02  Equatorial radius (km) 1,815  Equatorial radius (Earth = 1) 2.8457e-01  Mean density (gm/cm^3) 3.55  Mean distance from Jupiter (km) 421,600  Rotational period (days) 1.769138  Orbital period (days) 1.769138  Mean orbital velocity (km/sec) 17.34  Orbital eccentricity 0.004  Orbital inclination (degrees) 0.040  Escape velocity (km/sec) 2.56  Visual geometric albedo 0.61  Mean surface temperature -143°C  Magnitude (Vo) 5.02 

Data Table: Data Table: IoIo

• Io is the innermost Galilean satellite of Jupiter, and much like its siblings, is characterized by an extremely unique feature.

• During the Voyager encounters of the 1970s, initial pictures displayed an unusually young surface, the only body in the solar system with no substantial impact craters.

• As images were taken for navigation purposes, immense eruptive plumes were recorded inadvertently. Subsequent observations confirmed that Io is horded by volcanic activity.

• In October 1989, the artificial satellite Galileo was launched into orbit, its mission to recuperate a more detailed analysis of the Jovian system only viewed in flybys of the Voyager mission.

• Galileo reached within 900 km of Io's surface preceding the orbit insertion in 1995, however it did not revisit until October 11th 1999, as scientists thought the task too risky.

Satellite Images

Jupiter’s hold on Io is due to:

• The reason Galileo has spent less time observing Io is due to the danger to the spacecraft; Io lies deep in Jupiter's intense radiation belts.

• When the Galileo satellite recorded its images, it observed that as Io passed through Jupiter's shadow, it was outlined by a thin ring of glowing gas, illuminated by the impact of electrons from Jupiter's magnetosphere.

• As Jupiter rotates with its magnetosphere, it brushes by Io collecting with it about 1,000 kilograms (1 ton) of material per second.

• The ionized gases from Io's volcanic eruptions create a torus of plasma, resembling a doughnut shaped cloud around Jupiter, that is emanated by ultraviolet.

• The heavy ions in the torus migrate outward creating a pressure that inflates the Jovian magnetosphere, doubling its relative size.

• The more energetic sulphur and oxygen ions that fall along the magnetic field, and into the planet's atmosphere, are few that manage to result in auroras.

• Io acts as an electrical generator as it moves through the Jovian magnetic field, developing 400,000 volts across its diameter and generating an electric current of 3 million amperes that flows along the magnetic field into Jupiter's ionosphere.

• This hypothesis explains the active volcanism on Io as a result of Jupiter’s magnetic field, in turn amounting to the largest known electric circuit in the solar system.

THE MAGNETIC FIELDS OF GALILEAN SATELLITES

Io: Internal and Composition Speculation

• Io is relatively the size of the Earth’s moon.• Io’s violent volcanic activity has raised scientists curiosity, as recorded

average surface temperatures were around -143°C, a result of this satellite’s far distance from the sun, questioning the interior’s continuous molten state.

• Even though eruptions occur on Io at magnificently high temperatures, once the volcanic gases are emitted, they instantly freeze and condense.

• Even though Io exhibits an iron core, it is still only a minor amount of the overall content.

• The interior characteristics of the moon are inferred from gravity field and magnetic field measurements by the Galileo spacecraft.

• Io has a metallic (iron, nickel) core (shown in gray) drawn to the correct relative size. The core is surrounded by a rock shell (shown in brown). Io's rock or silicate shell extends to the surface. (© Copyright Calvin J. Hamilton)

Molten IoMolten Io• Io is Io is recognized as recognized as the most the most volcanically active body in the solarvolcanically active body in the solar systemsystem, , spewspewinging ~~100 times more lava 100 times more lava than than the the EarthEarth..

• This tormented satellite is governed This tormented satellite is governed by the magnetic forces of attraction by the magnetic forces of attraction from Jupiter and other surrounding from Jupiter and other surrounding satellites nearby.satellites nearby.

• Io's orbit around Jupiter is ellipIo's orbit around Jupiter is elliptical, tical, where thewhere the distance distance between thembetween them changes during a complete orbit. changes during a complete orbit. When Io is close to Jupiter, the When Io is close to Jupiter, the latter’s latter’s gravitygravity attempts to distort attempts to distort Io Io intointo an egg shape an egg shape. . The further The further away away from Jupiterfrom Jupiter Io reaches Io reaches, , the more it the more it relaxes relaxes ininto ato a spherical shape.spherical shape.

• In addition, the otherIn addition, the other large large Galilean satellitesGalilean satellites exert exert on Io on Io their their gravitational influencegravitational influencess, pulling it in other directions still, pulling it in other directions still, like a giant , like a giant tug-of-wartug-of-war..

• Io’s surficialIo’s surficial rising and falling rising and falling surface surface is relative to the is relative to the same forcesame forcess (gravity) that cause the rise and fall of tides o(gravity) that cause the rise and fall of tides off Earth's oceans Earth's oceans.. This This process isprocess is call calleded tidal flexingtidal flexing. .

• ThisThis flexing flexing creates bulges as big as 100 meters, creates bulges as big as 100 meters, producproducinging a a greatgreat frictionfrictional tensional tension, , where heat is generated and releases a significant where heat is generated and releases a significant amount of energy in violent amount of energy in violent volcanvolcanic eruptionsic eruptions..

Map projections: Io’s hot spots

Unimaginable HeatUnimaginable Heat

• Determination of Io’s heat capacity is bDetermination of Io’s heat capacity is based on how brightly the volcanoes glow at ased on how brightly the volcanoes glow at variablevariable visible and near-infrared wavelengths visible and near-infrared wavelengths, also, also a a necessary necessary measurement measurement of lava of lava composition.composition.

• Plumes from the volcanoes extend to more than 300 kPlumes from the volcanoes extend to more than 300 kmm(190 miles) above the surface, (190 miles) above the surface, with material being ejected at speeds up to a kwith material being ejected at speeds up to a kmm((00.6 miles) per second. .6 miles) per second.

• Typical Typical EarthEarth volcanoes volcanoes ejecteject basaltic basaltic lavalavass--iron, magnesium and calcium silicates rich --iron, magnesium and calcium silicates rich in the minerals olivine and pyroxene. in the minerals olivine and pyroxene.

• Basaltic melts typically have temperatures ranging from 1,300 to 1,450Basaltic melts typically have temperatures ranging from 1,300 to 1,450 in in Kelvin (1,050 Kelvin (1,050 to 1,200 degrees Celsius). to 1,200 degrees Celsius). Contrary-wiseContrary-wise, telescopic observations of Io several years ago , telescopic observations of Io several years ago suggested temperatures of 1,500 to 1,800 suggested temperatures of 1,500 to 1,800 in Kelvin.in Kelvin.

• ThThis hypothesis eliminated is hypothesis eliminated substances substances with low melting pointswith low melting points, such as liquid sulfur, , such as liquid sulfur, which which until then until then had been had been assumedassumed as a dominant volcanic fluid on Io. as a dominant volcanic fluid on Io.

• Galileo's measurements Galileo's measurements proved otherwise again, as Io’s lavas were reaching proved otherwise again, as Io’s lavas were reaching temperatures oftemperatures of 1,700 to 2,000 1,700 to 2,000 Kelvin, where magmaKelvin, where magma this hot has not been common on this hot has not been common on Earth for more than three billion years.Earth for more than three billion years.

• ““This discovery of high-temperature silicate volcanism provides us with an extremely This discovery of high-temperature silicate volcanism provides us with an extremely important clue to understanding the geophysical processes within Ioimportant clue to understanding the geophysical processes within Io”” quote quote McEwen. McEwen.

• Io Io provides scientists with the possible key into the provides scientists with the possible key into the Earth's geologic youth, when its Earth's geologic youth, when its interior temperatures were higher and the composition of the upper mantle interior temperatures were higher and the composition of the upper mantle differed differed from present days.from present days.

Io: in retrospectIo: in retrospect

• The camera and spectrometer The camera and spectrometer of Galileo of Galileo together have together have discovered a total of 41 hot spots on Iodiscovered a total of 41 hot spots on Io, where a total of , where a total of 60 are assumed.60 are assumed.

• Voyager 1 was able to observe nine colossal Voyager 1 was able to observe nine colossal eruptions on eruptions on its flyby, later verified by Voyager 2, where those visible its flyby, later verified by Voyager 2, where those visible were still violently active.were still violently active.

• Here are names of the most active volcanoes on Io: Here are names of the most active volcanoes on Io: Prometheus, Zamama, Masubi, Pillan Patera, Reiden Prometheus, Zamama, Masubi, Pillan Patera, Reiden Patera, Marduk, Pele, Ra Patera, Loki Patera, Patera, Marduk, Pele, Ra Patera, Loki Patera, and and Babbar Patera.Babbar Patera.

Cited Works:

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http://www.sciam.com/2000/0200issue/0200johnsonbox2.html

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