Earth: The Unique Planet in the Solar System

Learning Competencies

1. Recognize the uniqueness of Earth in the solar system with properties necessary to support life.
2. Explain that Earth consists of four subsystems across whose boundaries matter and energy flow.

Lesson 1: The Solar System

Key Points

• Location: Solar system located in the Milky Way’s Orion Star Cluster.
• Star Systems: Only 15% of stars in the galaxy host planetary systems. The Sun is one of those stars.
• Planets: Revolve around the Sun.
  • Categories:
    • Terrestrial Planets: Mercury, Venus, Earth, Mars
      • Made of rocky material
      • Solid surfaces
      • No ring systems
      • Few or no moons
      • Relatively small
    • Jovian Planets: Jupiter, Saturn, Uranus, Neptune
      • Gas Giants: Jupiter, Saturn (mainly helium and hydrogen)
      • Ice Giants: Uranus, Neptune (also contain rock, ice, water mixture)
      • Multiple moons
      • Have ring systems
      • No solid surface
      • Immense in size
  • Additional Features:
    • Asteroid Belt: Rocky objects including dwarf planet Ceres.
    • Kuiper Belt: Icy debris, dwarf planets like Pluto, comets.
    • Oort Cloud: Spherical collection of icy debris, considered edge of the solar system.

Exercise Questions

1. Closest planet from the Sun (Answer: Mercury).
2. Farthest planet from the Sun (Answer: Neptune).
3. Largest planet in the solar system (Answer: Jupiter).

Lesson 2: Dwarf Planets

Key Points

• Background: Discovery of multiple objects similar in size to Pluto.
• Criteria for Dwarf Planets: (IAU, 2006):
  1. Orbit the Sun.
  2. Sufficient mass to form a spherical shape.
  3. Did not clear their orbit of other objects (distinguishing them from planets).
• Recognized Dwarf Planets: Ceres, Pluto, Eris, Haumea, Makemake.

Exercise Question

• Name the five known dwarf planets: (Answer: Ceres, Pluto, Eris, Haumea, Makemake).

Lesson 3: Planet Earth

Key Points

• Formation: 4.5 billion years ago, from particles left over from the creation of the Sun.
• Structure:
  • Solid inner core
  • Liquid outer core
  • Mantle (flowing silica rocks)
  • Rocky crust
• Orbit: Third planet from the Sun, average distance 93 million miles.
• Unique Features:
  • Contains liquid surface water
  • Suitable distance from the Sun
  • Supports a large variety of life forms
• Evolution of Life:
  • Primitive microbial life 3.8 billion years ago
  • Millions of species cataloged
  • Many more species yet to be discovered

Exercise Question

• Reasons why Earth can sustain life: (Answers: Earth's position in the solar system, presence of water, presence of atmosphere).

Lesson 4: Earth Systems

Key Points

• Four Subsystems:
  • Atmosphere: Vapor layer of gases, 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide.
  • Hydrosphere: Includes all water, covering 71% of Earth.
  • Biosphere: Contains all life, overlaps with other spheres.
  • Lithosphere: Earth's crust and upper mantle, about 60 miles thick, contains tectonic plates.
• Interactions and Changes:
  • Volcanic eruptions impacting all spheres (magma in lithosphere, gases in atmosphere, lava changing biosphere, water condensation affecting hydrosphere).
  • Human beings interact with and depend on all four subsystems.