Overview
This lecture introduces the solar system, explains why Earth uniquely supports life, and describes Earth's four interacting subsystems.
The Solar System
- The solar system is located in the Milky Way's Orion star cluster.
- Only about 15% of stars in the galaxy have planetary systems.
- The Sun is orbited by eight planets, split into terrestrial and jovian types.
- Terrestrial planets (Mercury, Venus, Earth, Mars) are rocky, small, with few moons, and no rings.
- Jovian planets (Jupiter, Saturn, Uranus, Neptune) are gas or ice giants, large, have many moons, rings, and no solid surface.
- The asteroid belt lies between Mars and Jupiter; the Kuiper belt and Oort cloud are further out and contain icy bodies and dwarf planets.
Dwarf Planets
- Dwarf planets orbit the Sun and are massive enough to be nearly spherical.
- Unlike planets, dwarf planets have not cleared their orbits of other objects.
- The five recognized dwarf planets are Ceres, Pluto, Eris, Haumea, and Makemake.
- There may be hundreds more dwarf planets yet to be discovered.
The Uniqueness of Earth
- Earth formed about 4.5 billion years ago from solar system debris.
- Earth's structure includes an inner core, outer core, mantle, and crust.
- The Earth's distance from the Sun allows liquid water to exist on its surface.
- Earth's unique features: liquid water, correct position in the solar system, and a protective atmosphere.
- About 1.5 million species have been cataloged; many more remain undiscovered.
Earth's Subsystems
- Earth has four interacting subsystems: atmosphere (air), hydrosphere (water), lithosphere (land), and biosphere (life).
- The atmosphere contains nitrogen, oxygen, and trace gases, offering protection and supporting life.
- The hydrosphere covers 71% of Earth with water in all forms.
- The biosphere includes all living organisms and overlaps with the other subsystems.
- The lithosphere is the Earth's solid crust and upper mantle, about 60 miles thick.
- These subsystems interact continuously to maintain Earth's environment.
Key Terms & Definitions
- Terrestrial Planets — Rocky planets closest to the Sun (Mercury, Venus, Earth, Mars).
- Jovian Planets — Gas and ice giants farther from the Sun (Jupiter, Saturn, Uranus, Neptune).
- Dwarf Planet — A celestial body orbiting the Sun, nearly spherical, but not clearing its orbit.
- Atmosphere — The layer of gases surrounding Earth.
- Hydrosphere — All water on Earth, in liquid and solid forms.
- Lithosphere — The solid outer layer of Earth, including the crust and upper mantle.
- Biosphere — All living things on Earth.
Action Items / Next Steps
- Review the characteristics of each planet type and the four Earth subsystems.
- Prepare answers on why Earth sustains life, based on position, water, and atmosphere.
- Watch for next week's video and be ready for activities related to Earth systems.