Inner Planets
Chapter 20 Section 3
Pages 682-689
Inner Planets
• Terrestrial planets
• Small, solid planets
– Mercury
– Venus
– Earth
– Mars
Mercury
• 1st Planet
58,000,000km
• Rotation 59 Earth days
• Revolution 88 Earth
Days
• Extremely thin
atmosphere
– Fast moving, very hot,
molecules escaped
Mercury’s weak
gravitational pull.
Mercury
• Solid surface, many
flat planes and many
craters
• Greatest range of
temperature than any
other planet ( 430°C to
- 170°C)
• No moons
Venus
• 2nd Planet
108,000,000km
• “Evening Star”
• Similar in size and
density to Earth (“Earth’s
twin”)
• A solid, rocky, cratered
surface with volcanoes.
– 460ºC hot enough to melt
lead.
Venus
• “Rotates so slowly
(Rotation Period = 8
months) that its day
is longer that its year
(Revolution Period =
7.5 months)
• Rotates east to west
(retrograde rotation)
• No moons
Venus’s Atmosphere
• Never has a sunny day.
• Atmosphere so thick, the
pressure is 90 times that
on Earth.
• Atmosphere is mostly
carbon dioxide and
partially sulfuric acid.
– Clouds trap heat and
surface is 460°C
greenhouse effect
Earth
• 3rd Planet
150,000,000 km
– Rotation 24 Earth
hours
– Revolution 365.25
Earth Days
• 70% covered in water
– Supports life.
Earth
• As an atmosphere –
mostly 78% nitrogen and
21% oxygen
• 3 main layers – crust,
mantle and core
• Dynamic planet
(constantly changing)
• One natural satellite
called Moon.
Mars
• 4th Planet
228,000,000km
• “Red planet” – solid rocky
planet.
– Rotation 1.03 Earth Days
– Revolution- 687 Earth
Days
• Two moons – Phobos and
Deimos
Mars
• Mars has seasons because
it has a tilted axis
– winds stir up red soil causing
dust storms
– Frozen ice caps of carbon
dioxide at south pole and
frozen ice at north pole
during the winter season.
• Very thin atmospheremostly carbon dioxide