Solar System: Characteristics of Inner and Outer Planets

Solar System Overview

  • The solar system includes the sun, eight planets, moons, and smaller objects.
  • Planets revolve around the sun.
  • There are four inner and four outer planets.

Key Vocabulary

  • Gaseous
  • Molten
  • Revolution
  • Rotation
  • Ring

Inner Planets

  • Mercury, Venus, Earth, Mars.
  • Characteristics:
    • Small and rocky.
    • Dense.
    • Few moons (Mercury & Venus: none; Earth: 1; Mars: 2).
    • Slow rotation.
    • Fast revolution.

Mercury

  • Smallest, closest to the sun.
  • No moons.
  • Dense iron interior.
  • Virtually no atmosphere, huge temperature ranges.

Venus

  • Similar to Earth in size, mass, and density.
  • Rotates east to west (opposite).
  • Thick atmosphere (mostly carbon dioxide).
  • Hottest surface.

Earth

  • Rocky crust, molten mantle, iron/nickel core.
  • Only planet with liquid water on the surface.
  • Oxygen-rich atmosphere.

Mars

  • The "Red Planet" (iron-rich rust).
  • Thin carbon dioxide atmosphere.
  • Evidence of past liquid water.
  • Frozen water at poles.

Outer Planets

  • Jupiter, Saturn, Uranus, Neptune.
  • Characteristics:
    • Large gas giants (possibly with solid core).
    • Low density.
    • Many moons.
    • All have rings.
    • Fast rotation.
    • Slow revolution.

Jupiter

  • Largest, most massive planet.
  • Thick hydrogen/helium atmosphere.
  • More than 53 confirmed moons.
  • Great Red Spot (storm).

Saturn

  • Second largest, least dense.
  • Thick hydrogen/helium atmosphere.
  • More than 53 confirmed moons.
  • Largest, most visible rings.

Uranus

  • Ice giant.
  • Methane gives blue color.
  • At least 27 moons.
  • Rotates top to bottom (on its side).

Neptune

  • Ice giant.
  • Methane gives blue color.
  • Very active atmosphere.
  • At least 13 moons.

Planet Classification based on Composition

  • Inner Planets (Terrestrial):
    • Made of rocks and metals with hard surface.
    • Molten interior
    • Examples: Mercury, Venus, Earth, and Mars
  • Outer Planets (Gas Giants):
    • Made mainly of gas with no true surface.
    • Examples: Jupiter, Saturn, Uranus, and Neptune

Tectonic Activity

  • Earth is the only terrestrial planet with tectonic plates.
  • Gas giants do not have tectonic plates and do not experience tectonic activity.

Habitability

  • Water, temperature, atmosphere, and pressure are factors for habitability.
  • Earth is the only planet known to support life.
  • Mercury and Venus are uninhabitable due to extreme temperatures and atmospheric conditions.
  • Mars may have had life in the past.
  • Gas giants may harbor life on their moons.