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The Planets and the Solar System
Planets 2
” 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
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
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
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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
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).

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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
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
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
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
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,
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
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
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
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
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
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
Planets 9
Works Sited
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.


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