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
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.