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Origins: Earth is Born

Program Overview  Print this Teacher's Guide (PDF, 8 pages)

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NOVA traces Earth's geologic evolution.

The program:

• chronicles the formation of Earth from solar system dust particles that coalesced and became one of the four rocky planets closest to the sun.

• shows how scientists examine meteorites to determine the chemical composition of the dust grains that helped build Earth.

• explains that scientists estimate Earth to be about 4.6 billion years old, the average age of most meteorites discovered.

• describes the theory of the Iron Catastrophe, thought to have occurred almost 50 million years after Earth's formation, when internal heat from trapped radioactive elements and external heat from surface collisions caused the planet's iron to melt, sink, and form Earth's core.

• tells how convection currents in Earth's core generate the planet's magnetic field and relates the migration of Earth's magnetic north pole.

• looks at one theory of how the moon formed—a massive collision of Earth with a Mars-sized planetesimal produced debris that combined to form the moon some 50,000 years after Earth formed.

• reveals the finding that water may have been present about 200,000 years after Earth formed and details one theory that Earth's water came from comets.

• shows how scientists have tried to verify this theory through spectroscopy by examining and comparing the water in passing comets with that of Earth's water.

Taping Rights: Can be used up to one year after the program is taped off the air.