Earth's Atmosphere: Composition, Importance, Properties, and Layers

Composition of Earth's Atmosphere

  • The atmosphere is a thin layer of gas surrounding Earth that supports life.
  • Key components:
    • Nitrogen: ~75% of the atmosphere; helps living things make proteins.
    • Oxygen: ~25% of the atmosphere; needed for respiration and combustion; forms ozone.
    • Argon: 0.9% ; mostly unreactive.
    • Water Vapor: 0.04%; varies by location and time; important for weather.
    • Carbon Dioxide: 0.033%; essential for plant photosynthesis; levels have increased since the 1700s.
    • Trace Gases: Helium, neon, krypton, xenon.

Importance of the Atmosphere

  • Provides oxygen for survival.
  • Supplies water (rain and snow).
  • Traps energy from the sun, keeping Earth warm enough for liquid water to exist.
  • Ozone layer filters out harmful ultraviolet radiation.
  • Burns up most meteoroids before they can hit Earth's surface.

Properties of Air

  • Air is matter: it has mass, density, and pressure.
  • Density: The amount of mass in a given volume.
    • Formula for density: Density=MassVolumeDensity = \frac{Mass}{Volume}
  • Pressure: The force pushing on an area or surface due to the weight of the atmosphere.

Altitude Effects

  • Altitude: Height above sea level.
  • As altitude increases:
    • Air pressure decreases.
    • Density decreases.

Layers of the Atmosphere

  • Layers are classified based on changes in temperature.
    • Troposphere: 0-12 km; weather occurs here; temperature and pressure decrease with altitude.
    • Stratosphere: 12-50 km; contains the ozone layer; temperature increases with altitude; calmer air currents.
    • Mesosphere: 50-80 km; protects Earth from meteoroids; temperature decreases with altitude.
    • Thermosphere: 80+ km; very hot due to solar radiation; absorbs harmful x-rays; satellites orbit here; auroras occur here.
    • Ionosphere: 8-400 km; reflects radio waves using ions.
    • Exosphere: above 400 km; satellites relay phone calls and TV signals.

Tools to study the Atmosphere

  • LIDAR (Light Detection and Ranging):
    • Function: Uses light in the form of lasers instead of radio waves to detect objects.
    • Usage: Satellites equipped this instrument to send data back on clouds and particle in the atmosphere.
    • Example: CALYPSO ; launched in 02/2006