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Water; - delivered by comets 4.5 Byr ago
Comets delivered the volatiles (primarily water) to the inner
planets some 4 billion years ago, just after the formation of the
solar system.
Close up picture of the nucleus of comet Halley from
Giotto spacecraft
The extensive impact craters created early on during the
formation of the solar system has been eradicated on Earth by
weathering.
Atmosphere, weather driven by the Sun
Abundances of the Elements
Volcanoes
The Carbon Cycle
Carbon Dioxide (CO2) is a major constituent of the atmospheres
of both Mars and Venus, but not the Earth - Why?
Volcanoes outgas CO2 which dissolves in rainwater,
is washed into the oceans and combines with sea-shells
to become carbonates.
Plants also utilize CO2 in photosynthesis producing O2
This carbon cycle does not operate on Mars or Venus.
The presence of Life
Regulates the amount of Oxygen (O2)
Plants photosynthesize CO2 into O2, and N2
Greenhouse Effect
Carbon Dioxide
Global Warming?
Internal Structure resulting from
Chemical Differentiation
Plate Tectonics
Earth’s Major Plates
Collision of two plates
Geology - Igneous ( molten ) rocks
Geology - Sedimentary (layered) rocks
Metamorphic Rocks - modified by extreme temperatures
and pressures deep within the Earth’s crust
The Earth’s Magnetic Field
Protects Life on Earth from damaging Cosmic Rays
Aurora