Earth, Moon, and Mars Concepts

Earth

• Third planet from the Sun
• One large moon (5th largest in the solar system)
• Among only two objects in the solar system with surface liquids and a nitrogen-based atmosphere (Titan is the other)

Earth's Interior

• Core: High-density nickel and iron
• Mantle: Moderate density silicate rock
• Crust: Relatively low-density granite, basalt, etc.
• Lithosphere: Layer of cool, rigid rock; low-density rock "floats" on warmer, high-density rock below (similar to ice floating on water)

Heating and Differentiation of Earth's Interior

• Heat from the core is transported to the surface by convection cells in the mantle
• Heat is released into space as thermal radiation (infrared light)
• Planetary interiors cool over time

Planetary Magnetic Fields

• Created by moving charged particles
• Requires fluid interiors and rapid rotation for generation

Planetary Interiors in the Solar System

• Smaller planets cool more rapidly
• The Moon and Mars are geologically "dead"

Earth's Atmosphere

• Thickness: about 10 km (equivalent to the thickness of a sheet of paper when scaled to a globe)
• Composition:
  • 78% nitrogen
  • 21% oxygen
  • 1% trace gases

Greenhouse Effect vs. Temperature

• Visible light passes through the atmosphere and warms the surface
• The warm surface emits infrared light, which the atmosphere traps, preventing it from escaping into space
• Average surface temperature: 15°C (60°F); without greenhouse gas effect, it would be -16°C (3°F), leading to a "snowball Earth"

Major Greenhouse Gases

• Water vapor is the largest contributor to the greenhouse effect
• Carbon dioxide (CO2) is the next largest contributor
  • Both are trace gases and small increases have significant effects

Atmospheric Loss Mechanisms

• Gases can condense on the surface, thermally escape, or be blown away by the solar wind

Air Circulation Patterns

• Without rotation, hot air near the equator rises and cool air near the poles sinks, creating two large circulation cells
• Earth's spin causes variations in wind patterns, such as the Coriolis Effect
  • Northern hemisphere: storms spin counterclockwise

Earth's Moon (Luna)

• Often called "Luna"; lacks significant atmosphere and is geologically dead
• 5th largest moon in the solar system

Lunar Exploration

• First unmanned probe by Soviet Russia
• First human landing by the United States (Apollo 11: Neil Armstrong, Buzz Aldrin, Michael Collins)
• Recent missions: China's Chang'e lander (2013), India's Chandrayaan-3 (August 2023)

Lunar Maria

• Dark regions with few craters known as maria (Latin for "sea")
• Formed by lava from large impact craters, creating smoother surfaces

The Moon's Two Faces

• Near Side vs. Far Side
• Permanent shadows at the south pole where significant amounts of comet ice are found due to axial tilt differences

Concept Check

• Apollo 11 astronauts: Neil Armstrong, Buzz Aldrin, and Michael Collins

Preparation for Next Class

• Review textbook sections 11.1 and 11.2 (Jupiter’s moons)
• Complete homework set 08