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What Are the Main Gases in Earth's Lower Atmosphere?

According to NASA, the earth's atmosphere is divided into four major sections or "spheres." The lower atmosphere is known as the troposphere and extends up to nine miles into the air. All of the air that directly supports life on earth is found in the troposphere. All weather activity also occurs in this layer, which primarily consists of nitrogen and oxygen.

  1. Nitrogen

    • The lower atmosphere is approximately 78 percent nitrogen. The primary purpose of atmospheric nitrogen is to dilute the oxygen in the air. Nitrogen is not combustible, but oxygen is. The presence of nitrogen helps stabilize this combustibility. Nitrogen is odorless, tasteless and colorless. It is not poisonous, but it cannot sustain life on its own. Atmospheric nitrogen cannot be processed directly by plants and animals. It is pulled from the atmosphere by a specific type of bacteria, which then deposits it in the soil where it becomes a vital mineral in plant growth.

    Oxygen

    • The lower atmosphere is roughly 21 percent oxygen. Oxygen is the essential element that sustains life on earth. Plants produce oxygen through photosynthesis, a process that uses sunlight to convert water and carbon dioxide into glucose. Animals breathe in this oxygen, which, among other things, allows the body to process food for energy.

    Water Vapor

    • One of the most physically obvious components of the earth's lower atmosphere is water vapor. Depending on its intensity, water vapor can comprise up to 4 percent of the atmosphere. Water vapor causes the air to feel "muggy" on humid days. It also is visible in the form of fog and clouds. The condensation of water vapor in the air causes precipitation, which is also vital to live on earth.

    Trace Gases

    • The remaining percentage of the atmosphere is made up of argon, carbon dioxide, neon, helium, methane, hydrogen, nitrous oxide and ozone. The most common of these gases is argon, which makes up 0.93 percent of the lower atmosphere. The least common is ozone, which occupies only four parts per million in the lower atmosphere or 0.000004 percent. The majority of ozone in the earth's atmosphere is found above the lower atmosphere in the stratosphere.

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