Earth's Habitability in the Solar System

Solar System Overview

• Composed of the sun and eight major planets.
• Earth is the only planet known to support life.

Criteria for Habitability

• Two essential requirements for a planet to be habitable:
  • The star’s lifespan must be sufficient for life to develop; medium-mass stars, like the sun, fit this criterion.
  • The planet must be within the Goldilocks Zone, allowing for liquid water presence.

Goldilocks Zone

• Earth's distance from the sun ensures optimal temperature, avoiding extremes of too hot or too cold.
• Critical for sustaining liquid water, a vital element for life.

Planetary Conditions

• Mercury:
  • Too close to the sun, leading to extreme surface temperatures.
  • Thin atmosphere fails to retain heat.
• Venus:
  • Extremely hot due to a thick atmosphere caused by volcanic activity.
  • Enhanced greenhouse effect results in high surface temperatures.
• Mars:
  • Thin atmosphere and cold temperatures with minimal volcanic activity.
• Jovian Planets (Jupiter, Saturn, Uranus, Neptune):
  • Predominantly gas giants with no solid ground for life to exist.

Origin of Life on Earth

• 1952 experiment by Stanley Miller and Harold Urey simulated early Earth conditions, suggesting life began in oceans.
• Extremophiles: Organisms that survived harsh conditions such as extreme temperatures and pressures.

Oxygen Production

• Early Earth’s atmosphere lacked oxygen until cyanobacteria emerged.
• Cyanobacteria are credited with the first oxygen production through photosynthesis.
• Current oxygen levels rose significantly around 600 million years ago, cause of the increase remains uncertain.