Terrestrial Planets

There are four Terrestrial Planets in our Solar System. These Planets happen to be our closest neighbors and the closest to our Sun. They are also known as the Inner Planets. They are Mercury, Venus, Mars, and of course our home Earth. Scientists think that during the formation of our Solar System there were more than likely more Terrestrial Planetoids but that they either merged with each other or were destroyed.

Characteristics of a Terrestrial Planet:

  • Surface conditions may vary but they are made up of rocks or metals with a hard surface.
  • They have heavy metal cores.
  • None of the Terrestrial Planets in our solar systems have rings.
  • They have topological features like craters, valleys, and volcanoes.
  • They have shorter orbits around the Sun as they are closer to it.
  • They rotate slowly.
  • Have very few or no Moons. Earth has one, Mars has two.
Mercury – Photograph © NASA
Venus – Photograph © NASA


Named after the God of Commerce and Messengers (Roman). The first planet from our Sun and the smallest planet in our Solar System. He orbits the Sun every 88 Earth Days. Although he is close to the Sun, radar imaging has reviled highly reflective surfaces at both the poles which indicates the presence of ice in these areas. How is this possible? There are craters at both poles that are permanently in shadow which means that they are cold enough for ice to exist. His surface temperatures can vary wildly from an average of 430 degrees Celsius during the day to -180 degrees Celsius at night. This is because Mercury has a low surface gravity and solar winds constantly hit the Planet which means it doesn’t have much of an atmosphere so it can’t retain the heat at night.

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Emma Summers

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