The atmosphere is filled with gasses of nitrogen, oxygen, argon, and small amounts of lots of other compounds (like carbon-dioxide). Our lungs and bodies need oxygen in order to function normally. Many organisms (like humans) need oxygen to survive. An atmosphere is useful to our planet so that life can exist. If we didn't have an atmosphere, we wouldn't have air to breathe!

Another way in which the atmosphere helps life on Earth includes protection from the sun's energy. Our sun emits lots of types of energy called radiation, and most of this radiation is harmful to living organisms. Because the earth has an atmosphere, some of the harmful radiation from the sun is blocked before it reaches the earth's surface (where we live). Clouds--which exist in our atmosphere--are helpful in blocking some of the sun's energy from reaching us on the surface.

Some of the sun's energy is extremely important for life on the earth, like heat energy (which we call infrared radiation). Our atmosphere helps the earth stay warm by absorbing some of the sun's energy and re-emitting infrared radiation (heat) toward the surface (where you and I feel its warmth). Without our atmosphere, the earth would be much colder than it is today.