Water and the Origin of Life on Earth

The Early Earth and Absence of Water

• Initially, Earth may have lacked water.
• Early Earth's temperatures exceeded 100°C, causing any liquid water to boil away into space.

Theory of Water Delivery

• Asteroid Collision Theory: Water was delivered to Earth via large asteroids during its early formation.
• Earth experienced frequent asteroid impacts in its early years.
• As temperatures cooled, liquid water could be retained due to Earth’s position relative to the Sun.

Properties of Water

• Hydrogen Bonds: Present in liquid water, allowing it to absorb more heat before phase change.
• Earth’s gravitational pull helps retain water on its surface as oceans, lakes, and rivers.

Water on Mars

• Evidence suggests Mars once had water.
• Water may have reacted chemically with Martian sediment, resulting in hydration reactions that consumed available water.
• Earth's different sediment composition led to less water loss.

The Goldilocks Zone

• Refers to the optimal distance from a star where a planet can maintain liquid water.
• If too close, water vaporizes; if too far, water freezes.
• A "just right" distance allows temperatures between 0-100°C for liquid water.
• The size of the planet influences gravitational pull and atmospheric pressure.

Implications for Life

• All known life is based on leveraging liquid water.
• Many planets exist within the Goldilocks zone of their stars.
• Potential for other water-based life forms in the universe, similar to Earth.