EARTH’S PROTECTIVE SHELL Many planets including Earth have a protective layer of gases called an atmosphere Earth’s atmosphere helps keep the planet warm enough for living things to survive It also protects life on the planet from meteoroids and from certain harmful rays from the Sun and other stars From outer space layers of the atmosphere become visible 4
5 The atmosphere makes life on Earth possible Not only does it keep us warm but it holds the oxygen that animals use to breathe Other gases in the atmosphere help plants survive as well A meteoroid is a chunk of rock or metal from space Most meteoroids burn up as they pass through the atmosphere before they can hit the planet Without the atmosphere farms would not be able to make food
LAYERS OF THE ATMOSPHERE Scientists divide the atmosphere into five layers The layer closest to Earth is the troposphere It extends up to 11 miles 18 kilometers at its highest point above Earth’s surface The second layer is the stratosphere which extends to about 30 miles 50 kilometers above the surface The stratosphere contains the ozone layer The ozone layer blocks some of the harmful rays that come from the Sun These rays can cause skin cancer eye diseases and other health problems in people and other animals The third layer is the mesosphere It extends up 6 The clouds you can see in the sky are located in the troposphere
to about 50 miles 80 kilometers above Earth’s surface The fourth layer the thermosphere ranges from about 50 to 300 miles 80 to 480 kilometers above Earth The fifth and highest layer is the exosphere This layer ends where Earth’s gravity is too weak to prevent particles of gas from drifting into space Gravity is a pulling force that makes all objects attract other objects On Earth gravity pulls objects toward the center of Earth This is what makes objects fall It is also what gives objects weight 7 This drawing shows what can be found in each layer of the atmosphere
