Comparison Of The Planets

Abstract

Why is Earth the only planet in our solar system capable of sustaining life? Why is Earth the only planet in the solar system that has plentiful liquid water and an atmosphere that can protect the planet from the harmful ultra-violet rays of the Sun? What makes Earth so special? These are some of the questions that will be explored in greater detail as we use Comparative Planetology to understand what makes Earth a habitat for life and what makes it so different from the other planets in our solar system.

Earth As Compared to The Other Planets In Our Solar System

If we were to look at Earth as a starting point to compare the other eight planets in our solar system, the first thing we notice from space is the magnificent blue color and swirls of clouds. This is an inviting sight and is the first hint at why life is found on our planet. Earth has many features that the other planets do not have. Earth has many features that make it unique. Earth is made of rock and metal. It is one of the four terrestrial planets and has the largest Moon in the solar system. Earth has abundant volcanic activity because of its size in comparison to the other terrestrial planets. With the abundance of water and oxygen, Earth's atmosphere stays in balance and is able to continue supporting life. The liquid oceans help to remove carbon dioxide from the atmosphere and the presence of a stratosphere helps protect the surface from the deadly ultra-violet rays of the Sun. Another unique feature of Earth is plate tectonics. Plate tectonics acts as giant conveyor belt that moves the mantle of Earth around constantly changing the look of our planet. Although Earth's interior has not been explored nearly as much, scientists can tell about the composition of the deepest regions of Earth by using seismic waves following an earthquake. By reading this seismic data carefully, scientists get a better understanding of interior Earth.

In order to compare our planet to the other eight planets in our solar system, it is important to break them down by the two types of planets, terrestrial and Jovian. Terrestrial planets are more dense rocky planets, while Jovian planets have smaller cores, surrounded by large amounts of gas.

Terrestrial Planets

Mercury

Mercury is the smallest of the terrestrial planets and is closest to the Sun. With Mercury's small size the planet cooled much faster than Earth and it is for this reason that there is no volcanic activity. Bennett, Donahue, Schneider, and Voit (2004) There is also no air, wind, or atmosphere on Mercury. The proximity of Mercury to the Sun makes it unbearable with temperatures during the day rising to above 750 degrees Fahrenheit. At night the temperatures would fall to -240 degrees Fahrenheit. Mercury is very rich in metal with some rock. Since Mercury experienced a rapid cooling, the planet went through a phase of shrinking which did not give it much chance to capture enough water to support an atmosphere like Earth's.

Venus

Venus is very much like Earth in its size and composition. In the past before closer observation of this planet, it was thought that Venus could be the sister planet of Earth. Upon closer inspection it was discovered that Venus has a very thick atmosphere and acid rains fall from the sky, but never reach the ground because of the intense heat. Venus' atmosphere at the surface is the equivalent of 1 kilometer below the ocean on Earth. Arnett (2005) This thick atmosphere is thought to be caused by the slow rotation