Jupiter Moons

Jupiter Moons Jupiter, the largest of the Jovian planets, reigns supreme throughout the solar system. Named after the Roman god Jove, the ruler of Olympus; “Jupiter is the fifth planet from the sun and is also the largest planet in the Earth’s solar system. It is 318 times moremassive than Earth and is two thirds of the planetary mass in the solar system. Jupiter’s surface, unlike earth, is gaseous and not a solid. It is about 90% hydrogen and 10% helium with traces of methane, ammonia, water and rock.

Jupiter’s interior is very similar to the Sun’s interior but with a far lower temperature.”(Columbia) However, it is still unknown for certain, but Jupiter is believed to have a core of liquid metallic hydrogen. This exotic element can only be achieved at a pressure greater than 4 million bars. Jupiter radiates more energy in space than it receives from the sun. “Jupiter’s orbit lies beyond the asteroid belt at a mean distance of c.483 million mi (773 million km) from the sun; its period of revolution is 11.86 years.” (Seeds) In order from the sun it is the first of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), very large, massive planets of relatively low density, having rapid rotation and a thick, opaque atmosphere. “Jupiter has a diameter of 88,679 mi (142,800 km), more than 11 times that of the earth. Its mass is 318 times that of the earth and about 2 1/2 times the mass of allother planets combined.” (Columbia) A measurement of the diameter of Jupiter determined the planet’s polar flattening.

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The flattening of Jupiter was revealed by Pioneer to be slightly greater than that derived from the best Earth-based measurements. “The diameter of the planet was measured at a pressure of 800 mbar near the cloud tops (a bar is roughly equal to the pressure of 1 atm of Earth). Its polar diameter is 133,540 km (82,980 miles) and its equatorial diameter is142, 796 kilometers (88,732 miles).” (Seeds) These values were established by the timing of the occultation of the spacecraft by Jupiter. Thus, Jupiter is nearly 20 times more fattened than Earth, principally because of its non-solid state and its higher rate of rotation. The average density of Jupiter, calculated from its mass and volume, was confirmed as 1.33 gm/cm^3 (the density of water is 1). The atmosphere of Jupiter is composed mainly of hydrogen, helium, methane, and ammonia.

“It appears the atmosphere is divided into a number of light and dark bands parallel to its equator and shows a range of complex features, including an ongoing storm called the Great Red Spot, located in its southern hemisphere and measuring 16,150 mi long by 8,700 mi wide (26,000 by 14,000 km).” (Columbia) This Great Red Spot is still present in Jupiter’s atmosphere, more than 300 years later. It is now known that it is a vast storm, spinning like a cyclone. Unlike a low- pressure hurricane in the Caribbean Sea, however, the Red Spot rotates in a counterclockwise direction in the southern hemisphere, showing that it is a high-pressure system. “Winds inside this Jovian storm reach speeds of about 270 mph. The Red Spot is the largest known storm in the Solar System.

With a diameter of 15,400 miles, it is almost twice the size of the entire Earth and one-sixth the diameter of Jupiter itself.” (Fimmel) The Great Red Spot was first detected by Robert Hooke in 1664. Jupiter has no solid rock surface. One theory pictures a gradual transition from the outer ammonia clouds to a thick layer of frozen gases and finally to a liquid or solid hydrogen mantle. “The Spot and other markings of the atmosphere also provide evidence for Jupiter’s rapid rotation, which has a period of about 9 hr 55 min. This rotation causes a polar flattening of over 6%.” (Columbia) The temperature of Jupiter ranges from about -190 F (-124C) for the visible surface of the atmosphere, to 9 F (-13 C) at lower cloud levels; localized regions reach as high as 40 F (4 C) at still lower cloud levels near the equator.

Jupiter radiates about four times as much heat energy as it receives from the sun, suggesting an internal heat source. This energy is thought to be due in part to a slow contraction of the planet. Jupiter is also characterized by intense non-thermal radio emission; in the 15-m range it is the strongest radio source in the sky. Jupiter has a simple ring system that is composed of an inner halo, a main ring and a Gossamer ring. To the Voyager spacecraft, the Gossamer ring appeared to be a single ring, but Galileo imagery provided the unexpected discovery that Gossamer is really two rings. One ring is embedded within the other. The rings are very tenuous and are composed of dust particles kicked up as interplanetary meteoroids smash into Jupiter’s four small inner moons Metis, Adrastea, Thebe, and Amalthea.

Many of the particles are microscopic in size. “The innermost halo ring is toroidal in shape and extends radially from about 92,000 kilometers (57,000 miles) to about 122,500 kilometers (76,000 miles) from Jupiter’s center. It is formed as fine particles of dust from the main ring’s inner boundary ‘bloom’ outward as they fall toward the planet.” (A.U.R.A.) The main and brightest ring extends from the halo boundary out to about 128,940 kilometers (80,000 miles) or just inside the orbit of Adrastea. Close to the orbit of Metis, the main ring’s brightness decreases. “The two faint Gossamer rings are fairly uniform in nature.

The innermost Amalthea Gossamer ring extends from the orbit of Adrastea out to the orbit of Amalthea at 181,000 kilometers (112,000 miles) from Jupiter’s center.” (Hamilton) The fainter Thebe Gossamer ring extends from Amalthea’s orbit out to about Thebe’s orbit at 221,000 kilometers (136,000 miles). Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. “These particles and fields comprise the Jovian magnetosphere or magnetic environment, which extends 3 to 7 million kilometers (1.9 to 4.3 million miles) toward the Sun, and stretches in a windsock shape at least as far as Saturn’s orbit – a distance of 750 million kilometers (466 million miles).” (Seeds) Jupiter has a huge magnetic field, much stronger than Earth’s called the magnetosphere. The magnetosphere is not a true sense a perfect sphere. It is highly flattened due to the rapid rotation of Jupiter.

This magnetic field causes phenomenon such as strong lightening and even an aurora similar to earth’s aurora borealis. “Plasma flows in the dayside outer magnetosphere; the plasma rotates with the planet every 10 hours.” (Hamilton) Jupiter, unlike earth, has three distinct weather-producing zones or a troposphere. They are believed to contain Ammonia ice, ammonium hydrosulfide, and water and ice. “In the apparent or uppermost atmosphere, ammonia ice crystals thrive in a temperature of about 150 degrees Kelvin.” (A.U.R.A.) Most astronomers theorize that the next level of the atmosphere is primarily made up of Ammonium hydrosulfide crystals in a temperature of 200 degrees Kelvin. It is also theorized that the third and final level before the liquid metallic hydrogen is a layer of liquid ammonia and water droplets. Jupiter’s atmosphere is also plagued by high velocity winds that move in wide bands.

These winds blow in opposite directions along the latitude of the planet. Because of chemical reactions and differences, they can be seen wrapping around Jupiter in colorful bands. The light colored bands are called zones and the dark colored bands are called belts. It is not known whether the belts and zones are permanent; they have not changed in eighty years of observance. “One theory is that the jet stream at the belt-zone boundaries are linked to circulation patterns deep in the liquid interior” (Seeds). At least sixteen natural satellites are known to orbit Jupiter. Twelve of Jupiter’s moons are relatively small and seem to have been more likely captured than to have been formed in orbit around Jupiter.

They are conveniently divided into three groups. The four largest- -Io, Europa, Ganymede, and Callisto–were discovered by Galileo in 1610, shortly after he invented the telescope, and is known as the Galilean satellites. “These large moons are believed to have accreted as p …