MCQ Detailed View

The four planets known as terrestrial planets in our solar system are Mercury, Venus, Earth, and Mars. They are referred to as terrestrial (meaning "Earth-like") because they have solid, rocky surfaces similar to that of Earth, unlike the gas giants that consist mainly of hydrogen and helium.

These planets are called inner planets because they are located closer to the Sun and are separated from the outer planets by the asteroid belt. Their small size, high density, and solid surfaces distinguish them from the large gas planets further out.

Key characteristics of terrestrial planets:

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  Solid crust and mantle: Made primarily of silicate rocks and metals like iron and nickel.

  
  


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  Defined surfaces: They have mountains, valleys, craters, and in Earth's case, liquid water.

  
  


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  Thin or no atmospheres: Mercury has almost no atmosphere, while Earth and Venus have thicker ones.

  
  


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  Small in size: Compared to outer planets, terrestrial planets are smaller but much denser due to heavy elements in their composition.

  
  


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  Few moons: Earth has one natural satellite, Mars has two tiny moons, and Mercury and Venus have none.

  
  

These planets formed closer to the Sun during the early development of the solar system. The Sun's heat blew lighter gases like hydrogen and helium away from the inner region, allowing only heavier materials—rock and metal—to form planets. This explains why terrestrial planets are rocky and metallic, while outer planets (Jupiter, Saturn, Uranus, Neptune) became gas and ice giants.

The correct answer is Option A: Mercury, Venus, Earth, and Mars, because they share these Earth-like solid characteristics and are collectively known as the terrestrial or rocky planets.