The Inner Planets

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The Inner Planets

• Astronomy 1

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Weekly Quiz

• In place of a quiz this week, you must be able to
  identify each inner planet and give several facts
  for each.
• So pay attention!!!!

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• Inner Planets

• The 4 inner planets are small and have rocky
  surfaces
• They are known as the terrestrial planets
• The are more similar to each other than they are
  to the outer planets
• They all have a core, mantel and crust

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Earth

• 3rd planet from the sun
• Has an atmosphere about 100km above the Earths
  surface that has about 20 oxygen and about 78
  nitrogen
• The atmosphere and temperature range is suitable
  for water to exist as a liquid
• Approximately 70 is covered with water

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Earth

• Has enough gravity to hold most of the gas
  molecules (atmosphere)
• Geologically active because the internal heat
  allows for plate tectonics

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Mercury

• Closest planet to the sun
• Very small (not much larger than our moon)
• Has no moons of its own
• Geologically dead
• Has an iron core
• Very little is known about Mercury because it is
  so close to the sun
• Mariner 10 was a space probe that flew by in 1974
  -1975, but only got a few pictures

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Mercury

• Very little atmosphere because the sun heated the
  gas particles and they escaped into space
• Very extreme temperatures sun side reaches
  430C and at night falls to -170C (has the
  greatest temp range of all the planets)
• Takes 88 days to complete one revolution

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Venus

• 2nd planet from the sun
• Venus can often times be seen easily on Earth
  it appears to be a star, but is not because it is
  reflecting light from the sun
• It is the evening star because it can be seen in
  the west at sunset and the morning star because
  it can be seen in the east at sunrise
• It is known as the Earths twin because it is
  similar is size and composition however, it is
  very different in other aspects

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Venus

• Takes about 7.5 Earth months to revolve around
  the sun and about 8 months to rotate in its axis
• So that means that a day on Venus is longer that
  a year on Venus!
• It rotates opposite of other planets and moons in
  the solar system
• It rotates from east to west
• This is called retrograde rotation

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Venus

• Has a very thick atmosphere so thick that there
  is never a sunny day on Venus
• This causes the pressure to be 90 times greater
  than on Earth (it would crush you like a can!)
• The clouds are partly sulfuric acid
• Has volcanoes, but no other evidence of plate
  tectonics

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Venus

• Also because of the thick atmosphere the
  greenhouse effect is magnified on Venus
• The average surface temperature is 460C
• We have had more visits to Venus than any other
  planet 19 spacecrafts one even landed on the
  surface, but only survived for 23 minutes
• Scientists have mapped the surface of Venus and
  found many volcanoes and strange domes

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Mars

• 4th planet from the sun
• Called the Red Planet because it is red from
  the iron in the soil
• The atmosphere is mostly carbon dioxide (similar
  to Earth before life evolved)
• Has on about 1 of the pressure Earth has
• Has clouds, but only very thin ones

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Mars

• Mars is much colder than Earth because it is
  farther from the sun
• The south pole of Mars has frozen carbon dioxide
  or dry ice
• Mars has a tilted axis like Earth, therefore it
  has seasons like Earth
• Many spacecrafts have been sent to Mars a few
  have landed and traveled on Mars

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Mars

• Those probes are still on Mars that is why
  there have been no manned mission because
  scientists are unsure of how to safely return
  back to Earth
• Mars has two very small moons
• Phobos is only 27km wide (a car could travel
  across it in 15 minutes)
• Deimos is only 15km wide
• Both are covered in craters

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Mars

• Temperatures range from 35C to -170C
• There are strong winds that blow across the
  surface of Mars
• Last volcanic eruption was around 100 million
  years ago
• Olympus Mons is the largest volcano in the solar
  system