Earth
The only known planet to harbor life in the universe
The Third Planet from the Sun
Overview
Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land consisting of continents and islands, while the remaining 71% is covered with water.
Earth's atmosphere consists mostly of nitrogen and oxygen, which allows life to flourish by providing the necessary gases for respiration and creating a protective ozone layer that blocks harmful solar radiation.
Earth's outer layer is divided into several rigid tectonic plates that migrate across the surface over many millions of years, while its interior remains active with a solid iron inner core, a liquid outer core that generates the magnetic field, and a convecting mantle that drives plate tectonics.
Planetary Features
Earth is the largest and densest of the inner planets, the only one known to have plate tectonics, and the only planet where water exists in all three states (solid, liquid, and gas) on the surface.
Water Coverage
Oceans, seas, lakes, and rivers
Land Coverage
Continents and islands
Polar Ice
Of land area is covered by ice
The Cradle of Life
Earth is the only planet known to support life, with biodiversity that includes millions of species. The planet's biosphere has significantly altered Earth's atmosphere and other abiotic conditions, enabling the proliferation of aerobic organisms and the formation of the ozone layer.
Life on Earth likely began in the oceans about 3.8 billion years ago. The earliest evidence of life includes biogenic graphite and microbial mat fossils. Since then, the combination of Earth's distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive.
Earth's biodiversity reaches its peak in tropical rainforests, which are home to about half of the world's species. There are approximately 8.7 million species on Earth, with about 1.2 million documented and over 86% still awaiting description.
"Consider again that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every 'superstar,' every 'supreme leader,' every saint and sinner in the history of our species lived there—on a mote of dust suspended in a sunbeam."- Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space
Fascinating Facts About Earth
Water World
Earth is the only planet in our solar system with liquid water on its surface.
Protective Atmosphere
Our atmosphere protects us from meteoroids and harmful solar radiation.
Magnetic Field
Earth's magnetic field deflects solar winds that would otherwise strip away our atmosphere.
Perfect Rotation
Earth's 24-hour rotation and 23.5° tilt create stable seasons and climate patterns.
Earth in the Solar System
While Earth may seem large to us, it's just one of several terrestrial planets in our solar system:
Diameter: 6,779 km
53% the size of Earth
Diameter: 12,742 km
The largest terrestrial planet
Diameter: 12,104 km
95% the size of Earth
Earth is the largest of the four terrestrial planets (Mercury, Venus, Earth, and Mars) and has the highest density of any planet in our solar system.
Our Planetary Future
Earth's future is intrinsically tied to humanity's actions. Climate change, biodiversity loss, and resource depletion present significant challenges to the long-term health of our planet.
However, through sustainable practices, conservation efforts, and technological innovation, we have the potential to preserve Earth's habitability for future generations while expanding our presence into space.
As Carl Sagan reminded us, Earth is our only home in the vast cosmic arena. Preserving and cherishing this "pale blue dot" is perhaps our most important responsibility as a species.