Planet Mercury

Key notes

  • Mercury is the innermost planet of the Solar System.
  • It is the smallest planet.
  • It has no substantial atmosphere; it possesses a very thin exosphere.

  • It has:

    • The shortest orbital period: about 88 Earth days.
    • A 3:2 spin–orbit resonance.
    • A heavily cratered surface.
  • It has a large iron core relative to its size.
  • Mercury experiences extreme temperature variations.
  • It has no natural satellite and no ring system.
  • NASA’s MESSENGER mission studied Mercury extensively.
  • ESA–JAXA’s BepiColombo mission is studying Mercury.