Planetary Comparison

Planetary Comparison Paper

Properties of Earth

Earth is the fifth largest planet in our solar system and the third planet from the Sun. Earth's diameter is 12,756.3 km. Earth's average distance from the Sun is 149,600,000 km, and Earth has one moon. Earth is comprised of rock and metals.

Fortunately, for the inhabitants of Earth, Earth has an ozone layer which keeps dangerous solar radiation out and healthy oxygen in. The oxygen contained on the Earth enables the inhabitants to live and breathe. Oxygen makes up 20% of the gases in the Earth's atmosphere. The other gases include nitrogen, argon, and others.

Earth also consists of oceans, land, and snow capped mountains. In fact, water covers 71% of the Earth's surface. Because of the large amount of water versus the amount of dry land it is a wonder Earth is not called "Water" instead of Earth. Earth is the only planet where water is present on the surface in liquid form. Liquid water is responsible for most of the erosion and weathering of the Earth's continents which is a process that is unique in the solar system. (Arnett, 2006)

Earth is made up of layers; these layers are called the crust, mantle, and core. The crust differs in thickness in specific areas of the Earth. For example the crust is thinner under the oceans and thicker under the continents. (Arnett, 2006) Most of Earth's mass is in the mantle. The mantle consists of a layer of hot molten rock. This hot material rises through the crust and onto the Earth's surface when volcanos erupt. Earth's thick core consists primarily of iron and nickel with the outer core being liquid and the inner core probably being solid (Padilla, 2004)

How We Learn About Qualities of Earth and other Planets

We learn about the qualities of planets by explorations, observations, and comparative studies. Explanations must be based on observations, evidence, and testing. All knowledge gained should be peer reviewed and verified. One must also understand that the knowledge gained can and may change as new data is brought to light.

Planet Comparisons to Planet Earth

Mercury

Mercury, the smallest planet in the solar system, is the closest planet to the Sun. Mercury's diameter is 4,878 km, and Mercury has no moons.

Mercury is a barren, cratered planet with no volcanoes, no wind, no rain, and no life form. Regardless of its proximity to the Sun, Mercury has both hot and cold temperatures. Mercury contains iron just like planet Earth; however Mercury is made up of mostly iron whereas only about 35% of the Earth is comprised of iron.

Daytime temperatures on Mercury can reach up to 425 degrees Celsius and night temperatures can drop to -150 degrees Celsius. Mercury's atmosphere is thin. "Apparently the gasses Mercury once had were heated so much that then gas particles moved very fast. Since moving so fast, the gas particles escaped from Mercury's weak gravity into space." (Pidalla, 2004)

Venus

Venus is the second planet from the Sun. Venus is nearly the same size as Earth, and has even been called Earth's twin. Much of Venus's density and internal structure is very similar to Earth, yet in many other ways Venus is very different from Earth. Venus's average distance from the Sun is .72 AU. Venus is comprised of rocks and metal, and unlike Earth has no moons.

The atmosphere on Venus is so thick that Venus experiences a cloudy day everyday without ever having what we on Earth enjoy, a sunny day. "The pressure of Venus's atmosphere is 90 times greater than the pressure of Earth's atmosphere." (Pidalla, 2004) Venus's surface temperature can rise to nearly 470 degrees Celsius (approximately 880 degrees Fahrenheit). One could not breathe on Venus because the atmosphere is made up mostly of carbon dioxide, and the clouds are partly made up of sulfuric acid. "Venus probably once had large amounts of water like Earth but it all boiled away. Venus is now quite dry. Earth would have suffered the same fate had it been just a little closer to the Sun." (Arnett, 2006)

Like Earth, the surface of Venus has mountains, valleys, and volcanoes, but unlike Earth does not have oxygen or water.

Mars

Mars is fourth planet from the Sun and the last of the four inner planets. Mars's average distance from the Sun is 1.52 Au. Mars is comprised of rocks and metals and has two very small moons. Mars is only about half the size of Earth. Mar's moons are too small to affect anything Mars like the Moons on Earth affect the tides of the oceans.

Mars has large volcanoes, and great canyon, and polar caps made of frozen carbon dioxide and water ice. (Bennett, Donahue, Schneider, Voit, 2007)

"Mars has a very thin atmosphere composed mostly of the tiny amount of remaining carbon dioxide (95.3%) plus nitrogen (2.7%), argon (1.6%) and traces of oxygen (0.15%) and water (0.03%)." (Arnett, 2006) Mars has only 1% the pressure of the Earth's atmosphere. Mars also has clouds but they are much thinner than the clouds on Earth. Mars does not have an ozone layer like Earth, and therefore would leave one exposed to harmful, even deadly, ultraviolet rays from the Sun. However, the ozone layer is thick enough to sustain tough winds which have been known to cause large dust storms that surround the entire planet for sometimes months at a time. Mars's thin atmosphere does produce a greenhouse effect. However the greenhouse