Earth and Our Solar System

Earth is the only planet in our solar system that sustains life, and therefore one of the most intriguing planets because of its capabilities. Each of the seven other planets that orbit the same sun as Earth is interesting in its own way. Some planets share similar characteristics to those found on Earth, while other planets are completely different. An analysis of these terrestrial bodies, using comparative planetology, will allow us examine these qualities. However, before beginning such a process we must first gain a through understanding of the makeup of our own planet, Earth.

We begin by identifying two types of families of planets, rocky terrestrials and gaseous jovians. The latter planet made of gas with no solid surface. The atmospheres of these gaseous giants show a thicker density as you move closer to the core. However, unlike Earth’s rocky surface a gaseous jovian cannot be stood on. The four gaseous jovians in our solar system are Jupiter, Saturn, Neptune, and Uranus. Rocky terrestrials are the types of planets that possess a solid surface made of rock. Mars, Venus, and Mercury are examples of rocky terrestrials in our solar system. Of course, Earth is one of them as well.

Earth’s interior is comprised of three main layers, according to levels of density. The core consists of metals such as nickel alloy and iron and is known to be highly dense. The layer surrounding the core is called the mantle. This layer is less dense than the core and is very thick. The Earth’s mantle is made up of different minerals and has high ranges in temperatures. The third layer is the crust, a portion of mass that is very thin when compared to the other two layers. The crust is made up of basalt and granite, considered to be the lowest density rocks within all of the planet’s layers.

Scientists have the capabilities to determine the internal structure of our planet by using readings of seismic waves created by earthquakes. There are two different types of waves that travel through the Earth’s interior. They are primary waves (P waves) or secondary waves (S waves). Scientists study the speed at which they travel at and finally arrive at the other end of the planet. This process helps scientists determine what kind of materials the waves pass through along Earth’s interior. The factors, such as density, temperature, and pressure, of the different layers of our planet affect the speed at which these waves travel. It is these observations that allow researchers to gain a clear picture of what the inside of Earth is made up of.

Rocky terrestrials, such as Earth, Mars, and Venus, also share similar geological processes that create their shapes. An example of one of these processes is volcanism, which “refers to any eruption of molten lava onto the surface, whether it comes from a tall volcano or simply rises through a crack in a planet’s lithosphere (Bennett, p 258). As the lava erupts it eventually solidifies and creates new ground. Lava can be of a liquid form and run a great distance before solidifying, creating volcanic plains. It can also take on a thicker form that doesn’t travel as far but builds up around the opening that caused it to spill. This build up of new ground creates shield volcanoes and strato-volcanoes.

A second geological process that affects rocky terrestrials is impact cratering. These craters “form when an asteroid or comet slams into a world with a solid surface” (Bennett, p257). The incredible speed of the object making impact releases enough energy to shoot debris out from under the surface and crate a giant crater. This collision leaves a hole in the planet’s surface that is sometimes 10 times bigger than the object that caused the impact.

“Erosion is a blanket term for a variety of processes that break down or transport rock through the action of ice, liquid, or gas” (Bennett, p 260). Water is a powerful force here on Earth but not really found on other planets. Erosion on Mars, Venus or Mercury is mainly caused by wind or ice, elements that are also found on Earth. As these elements make their way through or around sand, dirt, or rock they create dunes, riverbanks, and valleys.

The lithosphere under the crust of a rocky terrestrial is broken up into large plates we call plate tectonics. This break up was caused by mantle convection, where rocks in that layer push against each other. This causes the plate tectonics to move around each other, or sometimes over and under other plates. “The movement of the plates explain nearly all Earth’s major geological features, including the arrangements of the continents, the nature of the seafloor, and the origin of earthquakes” (Bennett, p 260).

We have now seen the similarities between the interior structures of the rocky terrestrials, Earth, Mercury, Venus, and Mars. However, these planets