Planetary Physics A planet is a celestial body that revolves around a central star and does not shine by its own light ” (Grolier, 1992). The only planetary system that is known to man is our solar system. It is made up of nine planets which range in size and make-up. The nine major planets in our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. There are also many other minor planets which are also in our solar system, but they are unimportant compared to the nine major planets.
In this paper I will discuss the planets and how they are each unique. Mercury which is the planet that is closest to the sun is the first planet I will discuss. Mercury is the smallest of the inner planets. It is speculated that the heat from the sun made it impossible for the gases present to become part of the planetary formation. The surface of Mercury is extremely hot.
It is approximately 470 degrees celsius on the surface and is thought to be even hotter at the two ” hot spots.” These ” hot spots ” are on opposite ends of the equator. It is the heat of the surface that makes it impossible for Mercury to have any type of atmosphere. Mercury orbits the sun once every 88 days and has a true rotation period of 58.6 days. ” It is the closest planet to the sun and therefore orbits faster than any other planet ” (Thompson/Turk, 542, 1993). It is said that Mercury rotates three times for every two trips around the sun, so that during Planets 3 every alternate perihelon passage the same face points directly at the sun.
” Geologically, the most remarkable features of Mercury are compressional cliffs or faults, just the sort of wrinkles that might form in the crust if the interior of the planet shrank slightly ” (Morrison, 74, 1993). It is speculated that it was the solidification of Mercury’s metallic core that caused this global shrinkage. Mercury is also ” . . .
enriched in metal or depleted of rock ” (Morrison, 74, 1993). It is also believed that some of the inner core of Mercury is still in a fluid state. Scientists also believe that Mercury’s surface is made partially of silicate rock. The best way to describe Mercury is, ” . . .
small, heavily cratered and airless ” (Morrison, 71, 1993). Venus is the second closest planet to the sun and is said to ” . . . most closely resemble Earth in size, density, and distance from the sun ” (Thompson/Turk, 542, 1993).
Venus is known to most scientists as the sister planet to the Earth. It is called this because it closely resembles the Earth’s mass, density and diameter. The only thing different is that Venus ” is shrouded in thick clouds that completely hide the surface of the planet ” (Grolier, 1992). The surface temperature is also much warmer than that of Earth. Venus completes one revolution around the sun in 224.7 days.
This makes the Venusian day equal to 117 earth days. It is thought that this slow rotation may be the reason why Venus has no magnetic field. Planets 4 The atmosphere of Venus made up of 98% carbon dioxide and 2% Nitrogen. This atmosphere also has the presence of helium, neon and argon. This is yet another thing which makes Venus different from Earth.
The surface of Venus is quite a bit like that of the Earth. The surface has volcanoes and smooth plains. ” Much of the volcanic activity on Venus takes the form of Basaltic eruptions that inundate large ares, much as the mare volcanism flooded the impacted basins on the near side of the moon ” (Morrison, 93, 1993). One thing that differs from Earth is that there is no water liquid on the Venusian surface. Some of the scientific data that follows was taken out of Cattermole’s book.
The mean distance from the sun is 108.20 Km. The equatorial diameter is 12,012 Km and the equatorial rotation is 243 days. Finally the mass of Venus is 4.87*10^24 (Cattermole, 63, 1993). Venus, although different than Earth, is still our sister planet. Mars is the fourth furthest away from the sun and is recognized by its reddish color.
Mars is also very 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 thing that is very similar to Earth is the rotation period. Mars rotation period is only thirty seven minutes longer than the Earth’s. This would explain why Mars has significant seasonal changes just as Earth does. It is believed that the Planets 5 difference between winter and summer on Mars is even greater than on Earth.
Mars is extremely hard to understand due to the effect of blurring that is caused by the two atmospheres of Mars. Scientists do know, however, that Mars is relatively small and that changes take place in the surface features when the seasons change. It is also known that dust storms are prevalent and leaves the surface of Mars covered by a red haze. Mars has a very thin atmosphere which is composed of carbon dioxide, nitrogen, argon, water vapor and oxygen. Mars also has no magnetic field. ” Because the atmosphere of mars is so thin, wind velocities up to several hundred Km per hour are required to raise the dust particles during a dust storm, and these fast- moving particles erode structures with a sand-blasting effect ” (Grolier, 1992). Therefore, the surface is basically plain-like and covered with large craters.
There are also some areas where the rock is ” jumbled.” The poles of Mars are iced over and the temperature is about 160 – 170 degrees K. Mars also has its share of volcanoes. Most of these volcanoes are shield volcanoes. The surface is littered with winding channels that resemble river channels that have dried up over time. Scientists believe that water once existed and caused the formation of these channels.
It is said that, ” Mars remains the best candidate for life in the solar system outside of the Earth,” and that is what makes Mars so interesting to scientists. Jupiter is the fifth planet and is the most massive of all Planets 6 the planets in this solar system. ” Its mass represents more than two-thirds of the total mass of all the planets, or 318 times the mass of the Earth. Jupiters density is quite low at 1.3 g/cubic cm. The atmosphere of Jupiter contains water, ammonia, methane and carbon. It is thought by scientists that there are three cloud layers.
The wind activity on Jupiter is quite fierce and moves in jet streams parallel to the equator. The weather on Jupiter is still very hard for scientists to understand. There is not enough information to truly understand how the weather is on this planet. Jupiter is most known by the normal citizen by the rings it has. These ” rings are very diffuse.
The ring particles must generally be about as big as the wavelength of light, that is, only a few microns ” (Grolier, 1992). That is why these rings are faint or diffuse. The rings are what Jupiter is known for. Saturn is a planet which is also known for its rings and when viewed has a yellow or grayish color. The color is from the gaseous atmosphere and the dust particles in that atmosphere. The atmosphere is mostly a clear hydrogen-helium atmosphere.
There are also traces of methane, phosphine, ethane, and acetylene. This atmosphere is much different than that of the Earth’s. Saturn orbits the sun with a period of 29.4577 tropical years. It is 1.427 billion Km away from the sun and is therefore a cold planet. It has an equatorial diameter of 120,660 Km which Planets 7 makes it the second largest planet in our solar system.
The next planet is Uranus. The main problem scientists have with Uranus is that, “the lack of visible surface features means that it is difficult to measure the rotation period of Uranus “(Hunt/Moore, 388, 1983). Uranus has an equatorial diameter of 51,000 Km which is almost four times as much as Earth. The atmosphere is mostly methane gas and therefore the planet has a red tint or a blueish green color. Uranus also has rings but unlike Saturn these rings have almost no small particles.
Scientists are not as concerned with this planet. Neptune is the last of the gaseous planets in our solar system. Its atmosphere is much like Uranus’s because it is mostly helium and hydrogen. It also contains methane. Neptune has a diameter of 49,500 Km and a mass 17.22 times that of the Earth.
It has an average density of 1.67 /cm^3 (Grolier, 1992). Neptune also has rings like its other gaseous partners, but they are very faint. Not a great deal is known about Neptune. It is widely studied by scientists and that makes it an important planet. The final planet, which is also the smallest, and the furthest away from the sun is Pluto.
This planet is very hard to see therefore not a lot is known about its physical characteristics. Scientists do know that it has a thin methane atmosphere. Little is known about this planet because it is so far away from the Earth and the sun. Scientists are always learning new things and more data will arise in the future. Planets 8 As one can see the planets of most importance are the ones closest to the sun and Earth. Little is known about the far off planets therefore it is hard to give them full recognition.
Much is known about Mercury, Venus, Earth, Mars, Jupiter and Saturn. The other three planets are not as well known as these six are. Whether more planetary systems exist doesn’t really matter. There are still plenty of things we don’t understand about our own solar system. Scientists will have their work cut out for them in the future. Each and every planet has distinct differences and that helps show us how truly great God is. The planets will never fully be understood and will always be a great topic of discussion. Bibliography Cattermole, P.
(1995). Earth and Other Planets. New York: Oxford University Press. Grolier Electronic Publishing, Inc. (1992). Hunt, G.
& Moore, P. (1983). Atlas of the Solar System. Chicago: Rand Mc Nally & Company. Morrison, D. (1993). Exploring Planetary Worlds.
New York: Scientific American Library. Thompson, G. & Turk, J. (1993). Earth Science and the Environment.
New York: Saunders College Publishing & Harcourt Brace College Publishers.