Atmosphere

Space Ice

• The original stellar nebula included water.– Icy grains in protoplanets

• Half of Earth’s water from came from before the Sun.

Bill Saxton/NSF/AUI/NRAO

Oceans

• Oceans formed from gasses trapped in rocks and collisions from protoplanets.

• Surface water covers 75% of Earth.– Hydrosphere

Layers of Air

• The ionosphere includes gases broken into ions: 80-150 km.

• The mesosphere has falling temperatures with height: 50-80 km.

• The stratosphere is a stable layer of gas: 15-50 km.

• The troposphere is a dense, turbulent layer: up to 15 km high.

Blue Sky

• Air scatters high frequency light more than low frequency light.– Blue light higher

frequency than red

– Black when no scattered light at night

• Dust and water increase the scattering – less blue.

Composition of Earth’s atmosphere:

78.08% Nitrogen (N2)

20.95% Oxygen (O2)

0-4% Water (H2O)

0.93% Argon (Ar) 0.04% Carbon Dioxide

(CO2)

Greenhouse Effect

• The atmosphere only permits visible light and radio waves.

• Visible light warms the surface.

• The surface absorbs visible light and radiates infrared.

• The infrared is trapped and warms the air.

earth

atmospherevisible light

infrared light

Weather

• Planetary motion drives the weather.– Seasons from orbit

– Day-night temperature

– Wind circulation

• Weather is confined to the troposphere.

NOAA – January, 2014

Ozone

• High frequency UV light forms ozone from oxygen.– Stratosphere, mesophere

• Ozone concentrates in a layer in the stratosphere.– Opaque to UV-B

– Dissolved by CFCs

NASA

Magnetic Field

• The moving iron in the core creates a magnetic field.

• The magnetic field extends hundreds of kilometers above the surface.

• Particles from the sun are deflected by the field.

earthsolar wind

Aurora

• Charged particles from the sun can be trapped in the magnetic field.– Concentrated at the poles

– Air glows as an aurora

NASA, S. Vetter; aurora over Iceland