Image: Image of Earth taken by Apollo 8, the first mission to carry humans beyond Earth orbit between December 21, 1968 and December 27, 1968.
• Oxygen-Rich Atmosphere: Earth's atmosphere contains about 21% oxygen, which supports the respiration of life on Earth.
• Large amount of liquid water: Earth is the only planet known to have large amounts of liquid water on the surface, which supports life as we know it.
• A wide variety of climates and environments: Earth has a wide variety of climates and environments, ranging from hot deserts to tropical rainforests and cold polar regions.
• Rapid rotation: the Earth has a rapid rotation period, which means that it rotates on its axis in just under 24 hours.
• Strong Gravity: Earth's surface gravity is strong, about 9.8 m/s², which helps retain a dense atmosphere and keep liquid water on the surface.
• Protective Magnetic Field: Earth has a protective magnetic field that deflects much of the solar wind and charged particles, thereby shielding life on Earth from harmful radiation.
• Tectonic activity: the Earth has significant tectonic activity, with plates of the earth's crust in constant motion. This creates mountains, ocean trenches, volcanoes and earthquakes.
• Changing Atmosphere: The composition of Earth's atmosphere has changed over time, from a primitive oxygen-depleted atmosphere to today's oxygenated atmosphere.
• Complex system of life: Earth is home to a wide variety of life forms, ranging from microorganisms to animals and plants.
• Unique Moon: Earth has a unique moon, which plays an important role in the tides and cycles of life on Earth.
Planet Earth is a miraculous blue dot, an oasis of life amidst the vastness of an endless Universe. The age of the Earth is currently estimated at 4,550 million years. Earth is the only planet whose name does not come from a Roman or Greek God. Learn more.
Definition of the word planet (August 24, 2006):
"A planet is a celestial body which is in orbit around the Sun, which has sufficient mass so that its gravity overcomes the cohesive forces of the solid body and maintains it in hydrostatic equilibrium (spherical shape), and which has eliminated any body moving in a near orbit".