Earth and Its Uniqueness in the Solar System

Introduction

Focus on why Earth is the only planet known to sustain life.
Learning competencies:
1. Recognize Earth's uniqueness.
2. Explain Earth's subsystems and energy flow.

Location: Milky Way's Orion star cluster.
Star Systems: Only 15% of stars host planetary systems. Our sun is one of them.

Categories: Terrestrial and Jovian.
- Terrestrial Planets:
  - Mercury, Venus, Earth, Mars.
  - Characteristics: Rocky, solid surfaces, few/no moons, no rings, smaller size.
  - Mercury: Closest to the sun; shortest orbit (~3 months).
  - Venus: Hottest (up to 867°F); thick carbon dioxide atmosphere.
  - Earth: Only planet with liquid water, capable of sustaining life.
  - Mars: May have supported life 3.7 billion years ago.
- Jovian Planets:
  - Jupiter, Saturn (gas giants); Uranus, Neptune (ice giants).
  - Characteristics: No solid surface, multiple moons, and ring systems.
  - Jupiter: Largest planet in the solar system.
  - Saturn: Known for its wide rings.
  - Uranus: Rotates on its side.
  - Neptune: Coldest planet.

Asteroid Belt: Between terrestrial and jovian planets; remnants of solar system formation.
Kuiper Belt: Home to dwarf planets (e.g., Pluto).
Oort Cloud: Boundary of the solar system.

Definition: Objects that orbit the sun and are spherical but have not cleared their orbits.
Criteria: 1) Orbit around the sun, 2) Spherical shape, 3) Cannot clear orbit.
Recognized Dwarf Planets: Ceres, Pluto, Eris, Haumea, Makemake.
Potential: Hundreds more likely to be classified as dwarf planets.

Formation: Approximately 4.5 billion years ago from leftover particles of the sun.
Structure: Inner core, outer core, mantle, crust.
Distance from Sun: 93 million miles; optimal for sustaining life.

Liquid Water: Only known planet with liquid water on the surface.
Biodiversity: Home to 1.5 million known species and potentially millions more yet to be discovered.
Role of Water: Hydrates land, forms nutrient-rich soil, cycles moisture into the atmosphere.

Atmosphere: Thin layer of gases; protects from UV radiation and regulates temperature.
- Composition: 78% nitrogen, 21% oxygen, small amounts of argon and carbon dioxide.
Hydrosphere: All water on Earth (liquid and solid); covers 71% of the planet.
Biosphere: All living organisms; overlaps all other spheres.
Lithosphere: Earth's crust and upper mantle; changes due to tectonic movements.

Volcanic eruptions affect all spheres: magma from lithosphere, gases to atmosphere, lava affects biosphere, water changes hydrosphere.