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The Inner Planets
Chapter 14
The Inner Planets
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Mercury, Venus, Earth, and Mars
Inner Planets are small, dense and have rocky
surfaces.
Called “terrestrial” planets.
Earth
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Earth is made up of
three layers:
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Crust – the solid rocky
surface
Mantle – hot molten
rock
Core – dense inner layer
made of iron and nickel
Only planet with liquid
water
Earth’s gravity keeps
gases in to create our
atmosphere (mostly
oxygen and nitrogen)
Earth
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Mercury
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Smallest inner planet (not
much larger than Earth’s
moon)
Closest to the sun
Mercury’s surface has flat
plains and craters
Mercury has no atmosphere
because it has very little
gravity. Gases escape out
into space as they heat up.
Mercury has extreme
temperature difference (-170
°C to 430 °C) .
Mercury
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Venus
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Known as the ‘evening star’
because we can see it just
after sunset.
Its density and structure are
similar to Earth’s (Earth’s
twin)
Venus’s day is longer than
its year (day=8 months,
Year = 7.5 months)
Rotates from east to west
(opposite from other
planets). A possible
collision caused the change
in direction.
Venus
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Venus has a very thick atmosphere
Weight of it would crush you
 Mostly carbon dioxide
 Clouds are made of droplets of sulfuric acid
 Greenhouse effect traps the heat from the sun in
making Venus the hottest planet
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The surface of Venus is mostly rock with
volcanoes and plains formed by lava flows
Venus
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Mars
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The “red” planet from the
break down of iron-rich
rocks.
Atmosphere is more than 95
% carbon dioxide (similar to
Venus). It is so thin that
liquid cannot exist (would
turn to gas in the atmosphere
immediately)
Scientists believe that large
amounts of water once
flowed on Mars. This left
huge canyons and the
appearance of ancient
coastlines.
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Remaining water is frozen in
Mar’s polar icecaps.
Mars
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Mars has a tilted axis so it has a changing
seasons
Mars has 2 small moons (Phobos and Deimos)
Mars has giant volcanoes that appear to have
erupted in the past.
They are not active now
 Olympus Mons is the largest volcano in the solar
system (3 times the size of Mount Everest)
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Mars
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