The earth is only one small planet in an extremely large system of planets,satellites, asteroids, meteors and comets that revolve around the sun. Thissystem is referred to as the solar system. A planet is defined as a “celestialbody that revolves around a central star and does not shine by its own light” (Grolier,1992).
The only planetary system known to our civilization isour solar system. It is made up of nine planets that differ greatly size andphysical characteristics. The nine major planets in our solar system areMercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Thereare also many other minor planets which are also in our solar system, but theyare unimportant compared to the nine major planets.
Following are descriptionsof the differences that each of the nine planets have. The first planet to bediscussed is Mercury. Mercury is the planet that is closest to the sun at anaverage distance of about 58 million km, or about 36 million miles. It takes58. 7 days for Mercury to rotate. The planet rotates one and one half timesduring each revolution.
Mercury has a density and composition close to that ofEarth and, like Earth has a magnetic field. This magnetic field is produced fromthe planet’s outer core, which is said to be liquid iron. This liquid irongenerates a magnetic field with its movement. The atmosphere is extremely thinand contains sodium and potassium.
The photographs that have been taken ofMercury’s surface show the planet having craters and steep cliffs. Thetemperatures on Mercury reach amazingly high levels of about 430? C, which isabout 810? F on the side facing the sun and about -180? C, or about 290? F onthe side facing away from the sun. It is speculated that these hightemperatures, resulting from the planet’s proximity to the sun made itimpossible for the gases present to become part of the planetary formation orfor Mercury to have any type of atmosphere. Venus is the second closest planetto the sun and is said to most closely resemble Earth in size, density, anddistance from the sun. Venus is known as the sister planet to the Earth.
Onedifferences is that Venus is shrouded in thick clouds that completely hide thesurface of the planet. The surface temperature is also much warmer than that ofEarth. Venus completes one revolution around the sun in 224. 7 days.
This makesthe a day on Venus equal to 117 earth days. It is thought that this slowrotation may be the reason why Venus has no magnetic field. The atmosphere ofVenus made up of 98% carbon dioxide and 2% Nitrogen. This atmosphere also hasthe presence of helium, neon, and argon. The surface of Venus is quite a bitlike that of the Earth.
Cloud particles on Venus are mostly concentratedsulfuric acid. Water and water vapor are very uncommon on Venus. Many scientistshold the opinion that Venus, being close to the sun, was subjected to a kind ofextreme greenhouse effect. This effect caused any oceans to evaporate into theatmosphere. Another viewpoint that is held is that Venus had very little waterto begin with.
The surface has volcanoes and smooth plains. Much of the volcanicactivity on Venus takes the form of Basaltic eruptions that inundate largeareas, much as the mare volcanism flooded the impacted basins on the near sideof the moon. Because of the distances of the orbits of Venus and Earth from thesun, Venus can never be seen for than three hours before sunrise or three hoursafter sunset. When Venus is viewed through a telescope, it shows phases like themoon.
Venus rotates very slowly on its axis, in a direction that is opposite tothat of Earth. Cloud particles on Venus are mostly concentrated sulfuric acid. Water and water vapor are very uncommon on Venus. Many scientists hold theopinion that Venus, being close to the sun, was subjected to a kind of extremegreenhouse effect. This effect caused any oceans to evaporate into theatmosphere.
Another viewpoint that is held is that Venus had very little waterto begin with. Higher-level winds circle the entire planet at 360 km/hr. , or 225mph. However, even with these high velocity winds, near the planet’s surfacemore than half of Venus’s tremendously dense atmosphere is practically still.
From the surface up to 10 km, or 6 mi. altitude, wind speeds are only about 3 to18 km/hr, or about 2 to 11 mph. In the upper atmosphere, the night side of Venusis extremely cold. Day-side temperatures are 40? C, or 104? F but night-sidetemperatures are -170? C, or 274? F.
Scientists theorize that strong windsblow from the day side toward the near vacuum that is caused by the lowtemperatures on the night-side. Venus has huge active volcanoes, largesolidified lava flows, and a vast number of meteorite craters. The compositionof Venus’s dense atmosphere apparently prevents smaller meteorites from crashinginto the surface of the planet. A great deal of tectonic activity has takenplace on Venus, at least in the past.
Venus is the second closest planet to thesun and is said to ” . . . most closely resemble Earth in size, density,and distance from the sun “. Venus is often referred to by scientists asthe sister planet to the Earth. It is called this because it closely resemblesthe Earth’s mass, density and diameter.
The only thing different is that Venus” is shrouded in thick clouds that completely hide the surface of theplanet ” (Grolier, 1992). The surface temperature is also much warmer thanthat of Earth. Venus completes one revolution around the sun in 224. 7 days. Thismakes the Venusian day equal to 117 earth days. It is thought that this slowrotation may be the reason why Venus has no magnetic field.
Mars is the fourthfurthest away from the sun and is recognized by its reddish color. Mars is alsovery much like the Earth. ” More than any other planet in the solar system,Mars has characteristics that make it an Earth-like world “(Grolier, 1992). One similarity that Mars shares with Earth is the rotation period. Mars’rotation period is only thirty-seven minutes longer than Earth’s.
This explainsthe seasonal change similarity that Mars shares with Earth. It is said that thedifferences between winter and summer on Mars is more extreme than that onEarth. Mars is extremely hard to analyze and study due blurred effect that is adirect result of the two atmospheres of Mars. Scientists have been able todiscover that Mars is fairly small and that changes take place in the surfacefeatures upon seasonal changes.
The red haze that covers Mars is a result ofdust storms. The thin atmosphere of Mars is composed of carbon dioxide,nitrogen, argon, water vapor and oxygen. Mars is only one of the planets thatdoes not have a magnetic field. ” Because the atmosphere of mars is sothin, wind velocities up to several hundred Km per hour are required to raisethe dust particles during a dust storm, and these fast-moving particles erodestructures with a sand-blasting effect ” (Grolier, 1992). Therefore, thesurface is basically plain-like and covered with large craters. The poles ofMars are iced over and the temperature is about 160 – 170 degrees.
Mars sharesthe volcano characteristic with Venus. The surface is covered with windingchannels that resemble river channels that have dried up over time. Scientistsbelieve that water once existed and caused the formation of these channels. Itis said that, ” Mars remains the best candidate for life in the solarsystem outside of the Earth,” and that is what makes Mars so interesting toscientists, and what compels them to gain access to its surface as they once didthe moon. Jupiter is the fifth planet and is the most massive of all the planetsin this solar system. ” Its mass represents more than two-thirds of thetotal mass of all the planets, or 318 times the mass of the Earth.
Jupiter’smagnetic field is 14 times stronger than Earth’s. This magnetic field isresponsible for the huge belts of trapped charged particles that circle theplanet out to a distance of 10 million km. The atmosphere of Jupiter is made upof water, ammonia, methane and carbon. Scientists feel that there are threedifferent layers of clouds. The wind activity on Jupiter is volatile, and movesin jet streams parallel to the equator. The weather on Jupiter is still veryhard for scientists to understand.
There has not been nearly enough informationcompiled about conditions on Jupiter to truly understand, or describe the natureof the weather is on this planet. Its weather conditions remain something of amystery, or puzzle, to scientists. One feature of Jupiter that is recognizableby most individuals is its rings. These rings are very diffused and unclear. Thering particles are extremely small, approximately a few microns. The size of theparticles explains why the rings are not more clearly visible.
Sixteensatellites of Jupiter have been seen so far. Io and Europa, which are close toJupiter, are dense and rocky. Ganymede and Callisto, at greater distances, aremostly water ice at low densities. Callisto is almost as big as Mercury, andGanymede is bigger than Mercury. The surface of Europa is covered by a layer ofwater ice, and a layer of liquid water may lie beneath the ice.
Europa also hasa thin oxygen atmosphere. Io has volcanoes, powered by tides created in thissatellite’s interior by Jupiter’s gravitational force, that release hydrogensulfide and other sulfur compounds, giving it a mottled yellow, brown, and whitesurface. The remaining moons are very much smaller. Between Jupiter and Io arethe moons Metis, Adrastea, Amalthea, and Thebe. Outside Callisto are Leda,Himalia, Lysithea, Elara, Ananke, Carma, Pasiphae, and Sinope. Saturn is thesecond largest planet and is sixth in its distance from the sun.
Saturn isfamous for its rings, which first seen in 1610 by Italian scientist Galileo andidentified as rings by Dutch astronomer Christiaan Huygens in 1655. These”famous” rings contain more than 100,000 individual ringlets. The visiblerings stretch out to a distance of 136,200 km from Saturn’s center, but in manyareas they may be only 5 m thick. They are thought to contain rocks, frozengases, and water ice in lumps of various sizes from extremely small to large. One of Saturn’s rings is dense enough to block sunlight.
The atmosphere ofSaturn is predominantly made up of a clear hydrogen-helium atmosphere. Methane,phosphine, ethane, and acetylene are also identifiable in smaller amounts. Saturn orbits the sun with a period of 29. 4577 tropical years. It is 1. 427billion Km away from the sun and is therefore an extremely cold planet.
However,the gravitational situation of Saturn causes it to emit three times as much heatas it receives from the sun. Uranus is the seventh planet from the sun, and islocated between Saturn and Neptune. Uranus was discovered in 1781 by the Britishastronomer Sir William Herschel and was originally named Georgium Sidus, or theStar of George, in honor of King George III of Great Britain. The name Uranus,proposed by German astronomer Johann Elert Bode, was in use by the late 19thcentury.
Uranus has a diameter of 51,120 km, and its average distance from thesun is 2. 87 billion km. It has a mass greater than Earth’s. Uranus orbits thesun once every 84 years and rotates on its axis in 17 hours 15 minutes. Itsatmosphere is mostly hydrogen and helium, with a trace of methane. Through atelescope it appears as a blue-green disk with a faint green rim.
Nine ringsorbit Uranus, which also has 15 satellites revolving around its equator. Thelargest moons are named Oberon, Titania, Umbriel, Ariel, and Miranda. Eventhough there have been estimates made, the main problem scientists have withUranus is that this planet does not have visible surface features, which meansthat it is difficult to measure the rotation period of Uranus because they arenot sure which part of the planet they are viewing. Uranus has an equatorialdiameter of 51,000 Km which is almost four times as much as Earth. Theatmosphere is mostly methane gas and therefore the planet has a red tint or ablueish green color.
Uranus also has rings but unlike Saturn these rings havealmost no small particles. Scientists are not as concerned with this planet, andhave not determined that there are any significant scientific findings to bemade on its surface. Neptune is the last of the gaseous planets in our solarsystem. Neptune is the fourth largest planet in the solar system, and eighth inits distance from the sun. Its atmosphere is much like Uranus’s because itcontains predominantly helium and hydrogen.
It also contains methane which givesit its blue color. Neptune has a diameter of 49,500 Km and a mass 17 timesgreater than that of the Earth. Neptune is about 4. 5 billion km from the sun. Itis about 49,400 km in diameter, almost 4 times as wide as Earth. Neptune’sdeep atmosphere surrounds a liquid surface and a solid core.
Neptune rotates onits axis every 16 hours and orbits the sun in 164. 79 Earth years. Because of thelack of light on the planet It cannot be seen with the naked eye, but ratherrequires the usage of a telescope. Neptune has five thin rings and eight knownsatellites. The largest is of the satellites is Triton, with a diameter of 2705km, which is only slightly smaller than Earth’s moon. Triton has a nitrogenatmosphere, with some methane, and an active planetary surface with geysers.
Thesatellite Nereid has a diameter of about 320km. Neptune also has rings like itsother gaseous partners, but they are very faint. Not a great deal is known aboutNeptune. It is widely studied by scientists and that makes it an importantplanet. Pluto, the last planet to be discussed, is the smallest of the planetsand the farthest from the son. This planet, like Neptune, is not extremelyvisibly, and cannot be studied extensively.
Pluto is made of much rockiermaterial than are the other planets of the outer solar system. Many astronomersthink Pluto may be a former satellite of Neptune, which was possibly knockedinto a separate orbit during the early days of the solar system. is very hard tosee therefore not a lot is known about its physical characteristics. Scientistsdo know that it has a thin methane atmosphere. Little is known about this planetbecause it is so far away from the Earth and the sun.
Scientists are alwayslearning new things and more data will arise in the future. As one can see theplanets of most importance are the ones closest to the sun and Earth. Little isknown about the far off planets therefore it is hard to give them fullrecognition. Much is known about Mercury, Venus, Earth, Mars, Jupiter andSaturn. The other three planets are not as well known as these six are. Whethermore planetary systems exist doesn’t really matter.
There are still plenty ofthings we don’t understand about our own solar system. Scientists will havetheir work cut out for them in the future. Each and every planet has distinctdifferences and that helps show us how truly great God is. The planets willnever fully be understood and will always be a great topic of discussion. BibliographyCattermole, P.
(1995). Earth and Other Planets. New York: Oxford UniversityPress. Grolier Electronic Publishing, Inc. (1992).