A Comparison of the Planets in the Sol System

A Comparison of the Planets in the Sol System

Shaun J.

Sci350

December 19, 2004

Introduction

Beginning Mercury, this paper will compare the nine planets and major moons

of our solar system and describe their individual characteristics. At the

end of this discussion, the habitability factor of these different worlds

will be discussed as compared to that of the Earth's.

A Brief History of the Sol System

By radiocarbon dating meteorites, we know that roughly 4.6 billion years

ago our solar system began. This happens when a cloud of gas and dust were

disturbed and squeezed by perturbations of the surrounding space, possibly

caused by an exploding supernova. As the cloud began to contract and spin

around a common center of gravity, it also began to heat. After about 10

million years of condensing and heating, our solar system began to take

shape. Towards the center of the cloud, it was hot with cooler areas at the

edge. It is possible that this heating and cooling was even within the

cloud. A line called the frost line began to grow. Inside the frost line,

planetesimals made of rocks and metals began meshing and colliding, becoming

the terrestrial planets. Outside of the frost line, nebulae were accreting

around ices and would become the Jovian planets. The cloud further

contracted towards its center and eventually became hot enough to begin

nuclear fusion. This is the birth of our star, the Sun, and of our solar

system. Stellar winds from the ignition blew excess materials into the

fringes of our newly formed solar system as well as the interstellar medium.

The Nine Planets

During the accretion phase of the birth of our solar system, hundreds to

thousands of planetesimals congregated and coalesced. However, eight true

planets have survived to this day with the ninth possibly being the largest

of the Kuiper Belt objects. These planets are broken into two sections,

inner solar system and outer.

The Inner Solar System Planets and Moons

Mercury (The Messenger of the [Greek] gods)

Mercury is the smallest of the inner solar system planets is also the

closest to the sun. At .39 AU (1 AU = 93,000,000 miles), it orbits the sun

every 87.9 days, faster than any other planet in the solar system. Mercury

is composed of rocks and metal (iron mostly) and has a day temperature of

797o F and a nighttime temperature of -240o F. There is no atmosphere, no

volcanism, no signs of life and a heavily cratered surface. Mercury is about

a 5th the size of Earth. Some curious features of Mercury are the cracks

around its surface. Some of these cracks have created cliffs that are

thought to be the product of planetary shrinkage, which may have happened

early in Mercury's history when the core cooled and rather rapidly. Mercury

has no moon.

Venus (The goddess of Love)

Venus is the second largest planet within the inner solar system and second

from the sun at .72 AU with an orbital period of 225 days it is second

fastest around the sun. Venus is composed of rock and metal with an average

temperature of 850o F. This is due to the greenhouse effect produced by an

over abundance of carbon dioxide in its atmosphere. The atmosphere on Venus

has no oxygen and the pressure of its atmosphere is nine times that of Earth's

at ground level. There is evidence of volcanism in the past and the relative

present. Also, Venus has no water and no signs of life. A curious feature of

Venus is its squat volcanoes. This is possibly due to the massive pressure

of Venus' atmosphere on the ground. It is thought that when lava erupts from

within the planet, the pressure keeps the lava from spewing upwards.

Instead, it oozes out like tooth paste being slowly ejected from its tube.

Venus is just slightly smaller than Earth and has no moon.

Earth (ground, soil, dry land)

Earth is the largest planet in the inner solar system at a distance of 1 AU

from the sun with an orbit of one year and is third fastest around the sun.

Earth is composed of rock and metal with a varying degree of temperature

(depending upon where on Earth you are).The atmosphere is composed of

nitrogen, oxygen and carbon dioxide and has a layer