The Goldilocks Planet

Earth orbits in the habitable zone — the narrow band around a star where liquid water can exist on a planet's surface. But location alone is not enough. Earth's magnetic field shields the atmosphere from solar wind that would otherwise strip it away, as happened to Mars billions of years ago.

A Water World

Roughly 71% of Earth's surface is covered by water. That water acts as a massive heat sink, moderating temperature swings between day and night. Ocean currents also redistribute heat from the equator toward the poles, smoothing out the planet's climate.