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.