Exploring The Planets: Earth By Encyclopaedia Britannica, adapted by Newsela staff on 08.24.17 Word Count 632 Level MAX An image of Earth, created by the Suomi NFP Satellite. This photo is created from data collected by the satellite. It took four orbits around Earth! Photo from: NASA. Earth, our home planet, is the third planet from the sun. Earth travels around the sun at an average distance of about 93 million miles. It appears bright and bluish when seen from outer space. Earth has one natural satellite, called the moon, which orbits Earth at a distance of about 239,000 miles. Earth is the only planet in the solar system that can support life. Life is possible on Earth because the planet has water on its surface and oxygen gas in its air. Earth also has the ideal range of temperatures for life -- unlike Venus, it is not too hot, and unlike Neptune, it is not too cold. The average temperature on Earth is about 59 degrees Fahrenheit. This article is available at 5 reading levels at https://newsela.com. 1
Physical Features Earth, the fifth largest planet in the solar system, is made up of three layers: the core, the mantle and the crust. The core, or center of the planet, is about 4,300 miles across and is very hot. The mantle, which covers the core, is about 1,800 miles thick. The crust, Earth s thin, rocky outer layer, is approximately 19 miles thick at its thickest point. Plants, animals and people inhabit the crust. Land covers about 30 percent of Earth s surface and is divided into seven huge pieces, called continents. These continents are Africa, Antarctica, Asia, Australia, Europe, North America and South America. This article is available at 5 reading levels at https://newsela.com. 2
Water covers about 70 percent of Earth s surface in the form of oceans, rivers, lakes and groundwater. The four major water bodies on Earth are the Arctic, Atlantic, Pacific and Indian oceans. These oceans surround the continents. Some water on Earth is frozen. For example, there are large ice sheets in the Arctic and Antarctic regions. The layer of gases surrounding Earth is called the atmosphere. This is the air that living things breathe. Earth s atmosphere goes up to a few hundred miles above the surface, getting thinner as it gets farther from the surface. It contains mostly water vapor and the gases nitrogen (77 percent) and oxygen (21 percent). Orbit And Spin Like all planets, Earth has two types of motion: orbit and spin. Its orbit is the path it takes around the sun. One full trip around the sun takes Earth 365.25 days, which is equal to one calendar year. Earth also spins, or rotates around its axis. The axis is an imaginary line that runs through Earth s center from the North Pole to the South Pole. Earth completes one rotation in 24 hours, which is equal to one day. This article is available at 5 reading levels at https://newsela.com. 3
Earth Through Time Scientists theorize that Earth is about 4.6 billion years old. Earth s surface has changed greatly since it was first formed. Some changes have taken place over millions of years as wind and water have eroded, or worn away, the land. Erosion has created features such as the Grand Canyon. Other changes have happened very quickly. The force of an erupting volcano or an earthquake can change the surrounding land in just hours. The scientists who study these changes are called geologists. They have divided Earth s history into time periods called eons and eras. They use these periods to explain how and when changes on Earth took place. For instance, geologists have found that the Atlantic Ocean was formed during the Mesozoic era, a division of the Phanerozoic eon. This article is available at 5 reading levels at https://newsela.com. 4
Quiz 1 Which sentence from the section Orbit And Spin supports the idea that we use Earth s motion to determine a measurement of time? Like all planets, Earth has two types of motion: orbit and spin. One full trip around the sun takes Earth 365.25 days, which is equal to one calendar year. Earth also spins, or rotates around its axis. The axis is an imaginary line that runs through Earth s center from the North Pole to the South Pole. 2 Which sentence from the article supports the idea that NOT all changes to the earth happen quickly? Earth travels around the sun at an average distance of about 93 million miles. Earth completes one rotation in 24 hours, which is equal to one day. Some changes have taken place over millions of years as wind and water have eroded, or worn away, the land. They use these periods to explain how and when changes on Earth took place. 3 Which sentence from the article would be MOST important to include in a summary of the article? Earth, the fifth largest planet in the solar system, is made up of three layers: the core, the mantle and the crust. The crust, Earth s thin, rocky outer layer, is about 19 miles thick at its thickest point. For example, there are large ice sheets in the Arctic and Antarctic regions. Earth s atmosphere goes up to a few hundred miles above the surface, getting thinner as it gets farther from the surface. This article is available at 5 reading levels at https://newsela.com. 5
4 Read the following detail from the article. Life is possible on Earth because the planet has water on its surface and oxygen gas in its air. Earth also has the perfect range of temperatures for life unlike Venus, it is not too hot, and unlike Neptune, it is not too cold. The average temperature on Earth is about 59 degrees Fahrenheit. How does this detail develop the central idea of the article? It explains why the most important thing for life on Earth is water. It illustrates how other planets have the wrong type of air for life. It highlights the exact temperature needed to support life on Earth. It describes characteristics of Earth that make life on it possible. This article is available at 5 reading levels at https://newsela.com. 6