Jupiter Moons Essay Example For Students

Jupiter Moons Essay Jupiter, the largest of the Jovian planets, reigns supreme throughout the solarsystem. Named after the Roman god Jove, the ruler of Olympus; Jupiter isthe fifth planet from the sun and is also the largest planet in the Earthssolar system. It is 318 times moremassive than Earth and is two thirds of theplanetary mass in the solar system. Jupiters surface, unlike earth, is gaseousand not a solid. It is about 90% hydrogen and 10% helium with traces of methane,ammonia, water and rock. Jupiters interior is very similar to the Sunsinterior but with a far lower temperature.(Columbia) However, it is stillunknown for certain, but Jupiter is believed to have a core of liquid metallichydrogen. This exotic element can only be achieved at a pressure greater than 4million bars. Jupiter radiates more energy in space than it receives from thesun. Jupiters orbit lies beyond the asteroid belt at a mean distance ofc.483 million mi (773 million km) from the sun; its period of revolution is11.86 years. (S eeds) In order from the sun it is the first of the Jovianplanets (Jupiter, Saturn, Uranus, and Neptune), very large, massive planets ofrelatively 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 thatof the earth. Its mass is 318 times that of the earth and about 2 1/2 times themass of allother planets combined. (Columbia) A measurement of thediameter of Jupiter determined the planets polar flattening. The flattening ofJupiter was revealed by Pioneer to be slightly greater than that derived fromthe best Earth-based measurements. The diameter of the planet was measuredat a pressure of 800 mbar near the cloud tops (a bar is roughly equal to thepressure of 1 atm of Earth). Its polar diameter is 133,540 km (82,980 miles) andits equatorial diameter is142, 796 kilometers (88,732 miles). (Seeds)These values were established by the timing of the occultation of the spacecraftby Jupiter. Thus, Jupiter is nearly 20 times more fattened than Earth,principally because of its non-solid state and its higher rate of rotation. Theaverage density of Jupiter, calculated from its mass and volume, was confirmedas 1.33 gm/cm^3 (th e density of water is 1). The atmosphere of Jupiter iscomposed mainly of hydrogen, helium, methane, and ammonia. It appears theatmosphere is divided into a number of light and dark bands parallel to itsequator and shows a range of complex features, including an ongoing storm calledthe Great Red Spot, located in its southern hemisphere and measuring 16,150 milong by 8,700 mi wide (26,000 by 14,000 km). (Columbia) This Great RedSpot is still present in Jupiters atmosphere, more than 300 years later. It isnow 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 acounterclockwise direction in the southern hemisphere, showing that it is ahigh-pressure system. Winds inside this Jovian storm reach speeds of about270 mph. The Red Spot is the largest known storm in the Solar System. With adiameter of 15,400 miles, it is almost twice the size of the entire Earth andone-sixth the diameter of Jupiter itsel f. (Fimmel) The Great Red Spot wasfirst detected by Robert Hooke in 1664. Jupiter has no solid rock surface. Onetheory pictures a gradual transition from the outer ammonia clouds to a thicklayer of frozen gases and finally to a liquid or solid hydrogen mantle. The Spot and other markings of the atmosphere also provide evidence forJupiters rapid rotation, which has a period of about 9 hr 55 min. This rotationcauses a polar flattening of over 6%. (Columbia) The temperature ofJupiter ranges from about -190? F (-124?C) for the visible surface of theatmosphere, to 9? F (-13? C) at lower cloud levels; localized regions reach ashigh as 40? F (4? C) at still lower cloud levels near the equator. Jupiterradiates 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 toa slow contraction of the planet. Jupiter is also characterized by intensenon-thermal radio emission; in the 15-m range it is the strongest radio sourcein 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 ringappeared to be a single ring, but Galileo imagery provided the unexpecteddiscovery that Gossame r is really two rings. One ring is embedded within theother. The rings are very tenuous and are composed of dust particles kicked upas interplanetary meteoroids smash into Jupiters 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 fromabout 92,000 kilometers (57,000 miles) to about 122,500 kilometers (76,000miles) from Jupiters center. It is formed as fine particles of dust from themain rings inner boundary bloom outward as they fall toward the planet.(A Role Of Airplanes In World War II EssayIt orbits Jupiter every 7.2 days at a distance of 1.1 million km/700,000 mi. Its surface is a mixture of cratered and grooved terrain. Molecularoxygen was identified on Ganymedes surface in 1994 (Ganymede;Helicon). The space probe Galileo detected a magnetic field around Ganymede in 1996;this suggests it may have a molten core. (Hamilton). Galileo photographedGanymede at a distance of 7,448 km/4,628 mi. The resulting images were 17 timesclearer than those taken by Voyager 2 in 1979, and show the surface to beextensively cratered and ridged, probably as a result of forces similar to thosethat create mountains on Earth. Galileo also detected molecules containingboth carbon and nitrogen on the surface March 1997. Their presence may indicatethat Ganymede harbored life at some time (Hamilton). Callisto is theeighth of Jupiters known satellites and the second largest. It is the outermostof the Galilean moons and was discovered by Galileo and Marius in 1610. UnlikeGanymede, Callisto seems to have little internal structure; However, there aresigns from recent Galileo data that the interior materials have settledpartially, with the percentage of rock increasing toward the center. Callistois about 40% ic e and 60% rock/iron (Callisto;Helicon). Callistos surfaceis covered entirely with craters. The surface is very old, like the highlands ofthe Moon and Mars. Callisto has the oldest, most cratered surface of anybody yet observed in the solar system; having undergone little change other thanthe occasional impact for 4 billion years (Callisto;Helicon). Thelargest craters are surrounded by a series of concentric rings that look likehuge cracks but which have been smoothed out by eons of slow movement of theice. The largest of these has been named Valhalla (right). 4000 km in diameter,Valhalla is a dramatic example of a multi-ring basin, the result of a massiveimpact (Callisto;Helicon). In terms of the mass of Earths Moon,the masses of the Galilean satellites in order of distance from Jupiter werefound to be: Io, 1.21; Europa, 0.65; Ganymede, 2.02; and Callisto, 1.46. Themass of Io was 23% greater than that estimated before the Pioneer odyssey. Thedensity of the satellites decreases wit h increasing distance from Jupiter andwas refined as a result of Pioneers observations. Ios density is 3.52;Europas, 3.28; Ganymedes, 1.95; and Callistos, 1.63 gm/cm^3. The outersatellites, because of their low density, could consist largely of water andice. All four satellites were found to have average daylight surfacetemperatures of about-140 C (-220 F) (Columbia). A second group iscomprised of the four innermost satellitesMetis, Adrastea, Amalthea, and Thebe. Discovered by E. E. Barnard in 1892, Amalthea has an oblong shape and is 168 mi(270 km) long. Metis and Adrastea orbit close to Jupiters thin ring system;material ejected from these moons helps maintain the ring. The final groupconsists of the eight remaining satellites, none larger than c.110 mi (180 km)in diameter. Four of the outer eight satellites located from 14 million to16 million mi from Jupiter (22 million-26 million km), have retrograde motion,i.e., motion opposite to that of the planets rotation. The other four havedirect orbits. It is speculated that all eight might be captured asteroids(Seeds). When it is in the nighttime sky, Jupiter is often the brighteststar in the sky (it is second only to Venus, which is seldom visiblein a dark sky). The four Galilean moons are easily visible with binoculars; afew bands and the Great Red Spot can be seen with a small astronomicaltelescope. Jupiter is very gradually slowing down due to the tidal drag producedby the Galilean satellite s. How will this effect it and its moons? We currentlyknow that the same tidal forces that are slowing Jupiter down are changing theorbits of the moons, very slowly forcing them farther from Jupiter. Asadditional data is gathered and technology enables a new fronitier, only thenwill we know the fate of Jupiter. Until then we can merely speculate its finallife as a Jovian planet. BibliographyBibliography The Columbia Encyclopedia, Fifth Edition. Copyright ?1993,Columbia University Press. Licensed from Lernout ; Hauspie Speech ProductsUSA, Inc. Pioneer: First to Jupiter, Saturn, and Beyond: Chapter 6A Results AtThe New Frontier; Fimmel, Richard O.; Van Allen, James; Burgess, Eric;09-01-1990 Ganymede; ( The Hutchinson Dictionary of Science ) ; 01-01-1998,Helicon Publishing Ltd. 1998. Io ; ( The Hutchinson Dictionary of Science ) ;01-01-1998, Helicon Publishing Ltd. 1998. Callisto; ( The Hutchinson Dictionaryof Science ) ; 01-01-1998, Helicon Publishing Ltd. 1998. Europa; ( TheHutchinson Dictionary of Science ) ; 01-01-1998, Helicon Publishing Ltd. 1998. Seeds, Michael A., Foundations of Astronomy; copyright 1994, Wadsworth Inc. Copyright ? 1997-1999 by Calvin J. Hamilton. Copyright ? 1998 The Associationof Universities for Research in Astronomy, Inc. Author not available, Astronomy:Common Terms in Astronomy. , The New York Public Library Science Desk Reference,01-01-1995.