FREE ESSAY ON THE PLANETS/SOLAR SYSTEM

THE PLANETS/SOLAR SYSTEM

The earth is only one small planet in an extremely large system of planets, satellites,
asteroids, meteors and comets that revolve around the sun. This system is referred to as
the solar system. A planet is defined as a "celestial body that revolves around a central
star and does not shine by its own light  (Grolier,1992). The only planetary system known
to our civilization is our solar system. It is made up of nine planets that differ
greatly size and physical characteristics. 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. Following are descriptions of the differences that
each of the nine planets have. 
The first planet to be discussed is Mercury. Mercury is the planet that is closest to the
sun at an average distance of about 58 million km, or about 36 million miles. It takes
58.7 days for Mercury to rotate. The planet rotates one and one half times during each
revolution. Mercury has a density and composition close to that of Earth and, like Earth
has a magnetic field. This magnetic field is produced from the planet's outer core, which
is said to be liquid iron. This liquid iron generates a magnetic field with its movement.
The atmosphere is extremely thin and contains sodium and potassium. The photographs that
have been taken of Mercury's surface show the planet having craters and steep cliffs. 
The temperatures on Mercury reach amazingly high levels of about 430? C, which is about
810? F on the side facing the sun and about -180? C, or about 290? F on the side facing
away from the sun. It is speculated that these high temperatures, resulting from the
planet's proximity to the sun made it impossible for the gases present to become part of
the planetary formation or for Mercury to have any type of atmosphere.
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. Venus is known as the sister planet to the
Earth. One differences is that Venus is shrouded in thick clouds that completely hide the
surface of the planet. 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 a day on
Venus equal to 117 earth days. It is thought that this slow rotation may be the reason
why Venus has no magnetic field. 
The atmosphere of Venus made up of 98% carbon dioxide and 2% Nitrogen. This atmosphere
also has the presence of helium, neon, and argon. The surface of Venus is quite a bit
like that of the Earth. Cloud particles on Venus are mostly concentrated sulfuric acid.
Water and water vapor are very uncommon on Venus. Many scientists hold the opinion that
Venus, being close to the sun, was subjected to a kind of extreme greenhouse effect. This
effect caused any oceans to evaporate into the atmosphere. Another viewpoint that is held
is that Venus had very little water to begin with.
The surface has volcanoes and smooth plains. Much of the volcanic activity on Venus takes
the form of Basaltic eruptions that inundate large areas, much as the mare volcanism
flooded the impacted basins on the near side of the moon. Because of the distances of the
orbits of Venus and Earth from the sun, Venus can never be seen for than three hours
before sunrise or three hours after sunset. When Venus is viewed through a telescope, it
shows phases like the moon. Venus rotates very slowly on its axis, in a direction that is
opposite to that of Earth.
Cloud particles on Venus are mostly concentrated sulfuric acid. Water and water vapor are
very uncommon on Venus. Many scientists hold the opinion that Venus, being close to the
sun, was subjected to a kind of extreme greenhouse effect. This effect caused any oceans
to evaporate into the atmosphere. Another viewpoint that is held is that Venus had very
little water to begin with.
Higher-level winds circle the entire planet at 360 km/hr., or 225 mph. However, even with
these high velocity winds, near the planet's surface more 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 to 18 km/hr, or about 2 to 11 mph. In the
upper atmosphere, the night side of Venus is extremely cold. Day-side temperatures are
40? C, or 104? F but night-side temperatures are -170? C, or 274? F. Scientists theorize
that strong winds blow from the day side toward the near vacuum that is caused by the low
temperatures on the night-side.
Venus has huge active volcanoes, large solidified lava flows, and a vast number of
meteorite craters. The composition of Venus's dense atmosphere apparently prevents
smaller meteorites from crashing into the surface of the planet. A great deal of tectonic
activity has taken place on Venus, at least in the past. 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 . Venus is often referred to by 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. 
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 similarity
that Mars shares with Earth is the rotation period. Mars' rotation period is only
thirty-seven minutes longer than Earth's. This explains the seasonal change similarity
that Mars shares with Earth. It is said that the differences between winter and summer on
Mars is more extreme than that on Earth. Mars is extremely hard to analyze and study due
blurred effect that is a direct result of the two atmospheres of Mars. Scientists have
been able to discover that Mars is fairly small and that changes take place in the
surface features upon seasonal changes. The red haze that covers Mars is a result of dust
storms.
The thin atmosphere of Mars is composed of carbon dioxide, nitrogen, argon, water vapor
and oxygen. Mars is only one of the planets that does not have a 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. 
The poles of Mars are iced over and the temperature is about 160 - 170 degrees. Mars
shares the volcano characteristic with Venus. The surface is covered 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, and what compels them to gain
access to its surface as they once did the moon.
Jupiter is the fifth planet and is the most massive of all 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. Jupiter's magnetic field is 14 times stronger than
Earth's. This magnetic field is responsible for the huge belts of trapped charged
particles that circle the planet out to a distance of 10 million km. The atmosphere of
Jupiter is made up of water, ammonia, methane and carbon. Scientists feel that there are
three different layers of clouds. The wind activity on Jupiter is volatile, and moves in
jet streams parallel to the equator. 
The weather on Jupiter is still very hard for scientists to understand. There has not
been nearly enough information compiled about conditions on Jupiter to truly understand,
or describe the nature of the weather is on this planet. Its weather conditions remain
something of a mystery, or puzzle, to scientists. One feature of Jupiter that is
recognizable by most individuals is its rings. These rings are very diffused and unclear.
The ring particles are extremely small, approximately a few microns. The size of the
particles explains why the rings are not more clearly visible. 
Sixteen satellites of Jupiter have been seen so far. Io and Europa, which are close to
Jupiter, are dense and rocky. Ganymede and Callisto, at greater distances, are mostly
water ice at low densities. Callisto is almost as big as Mercury, and Ganymede is bigger
than Mercury. The surface of Europa is covered by a layer of water ice, and a layer of
liquid water may lie beneath the ice. Europa also has a thin oxygen atmosphere. Io has
volcanoes, powered by tides created in this satellite's interior by Jupiter's
gravitational force, that release hydrogen sulfide and other sulfur compounds, giving it
a mottled yellow, brown, and white surface. The remaining moons are very much smaller.
Between Jupiter and Io are the moons Metis, Adrastea, Amalthea, and Thebe. Outside
Callisto are Leda, Himalia, Lysithea, Elara, Ananke, Carma, Pasiphae, and Sinope. 
Saturn is the second largest planet and is sixth in its distance from the sun. Saturn is
famous for its rings, which first seen in 1610 by Italian scientist Galileo and
identified as rings by Dutch astronomer Christiaan Huygens in 1655. These "famous" rings
contain more than 100,000 individual ringlets. The visible rings stretch out to a
distance of 136,200 km from Saturn's center, but in many areas they may be only 5 m
thick. They are thought to contain rocks, frozen gases, 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 of Saturn 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 1.427 billion 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 heat as it receives from the
sun.
Uranus is the seventh planet from the sun, and is located between Saturn and Neptune.
Uranus was discovered in 1781 by the British astronomer Sir William Herschel and was
originally named Georgium Sidus, or the Star 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 19th century.
Uranus has a diameter of 51,120 km, and its average distance from the sun is 2.87 billion
km. It has a mass greater than Earth's. Uranus orbits the sun once every 84 years and
rotates on its axis in 17 hours 15 minutes. Its atmosphere is mostly hydrogen and helium,
with a trace of methane. Through a telescope it appears as a blue-green disk with a faint
green rim.
Nine rings orbit Uranus, which also has 15 satellites revolving around its equator. The
largest moons are named Oberon, Titania, Umbriel, Ariel, and Miranda. 
Even though there have been estimates made, the main problem scientists have with Uranus
is that this planet does not have visible surface features, which means that it is
difficult to measure the rotation period of Uranus because they are not sure which part
of the planet they are viewing. 
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, and have not
determined that there are any significant scientific findings to be made on its surface.
Neptune is the last of the gaseous planets in our solar system. Neptune is the fourth
largest planet in the solar system, and eighth in its distance from the sun. Its
atmosphere is much like Uranus's because it contains predominantly helium and hydrogen.
It also contains methane which gives it its blue color. Neptune has a diameter of 49,500
Km and a mass 17 times greater than that of the Earth. Neptune is about 4.5 billion km
from the sun. It is about 49,400 km in diameter, almost 4 times as wide as Earth.
Neptune's deep atmosphere surrounds a liquid surface and a solid core. 
Neptune rotates on its axis every 16 hours and orbits the sun in 164.79 Earth years.
Because of the lack of light on the planet It cannot be seen with the naked eye, but
rather requires the usage of a telescope. 
Neptune has five thin rings and eight known satellites. The largest is of the satellites
is Triton, with a diameter of 2705 km, which is only slightly smaller than Earth's moon.
Triton has a nitrogen atmosphere, with some methane, and an active planetary surface with
geysers. The satellite Nereid has a diameter of about 320km. 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. 
Pluto, the last planet to be discussed, is the smallest of the planets and the farthest
from the son. This planet, like Neptune, is not extremely visibly, and cannot be studied
extensively. Pluto is made of much rockier material than are the other planets of the
outer solar system. Many astronomers think Pluto may be a former satellite of Neptune,
which was possibly knocked into a separate orbit during the early days of the solar
system. 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.
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
Works Cited
Cattermole, P. (1995). Earth and Other Planets. New York: Oxford University Press.
Grolier Electronic Publishing, Inc. (1992).