Earth

Earth is the third planet from the Sun, and the only planet known to harbor life.

Characteristics
Earth is a terrestrial planet in the Solar System. 70% of the planet's surface is covered in liquid water, and 30% is covered in various land types. Earth is the densest planet of the Solar System.

Atmosphere
Earth's atmosphere is roughly 78% Nitrogen, 21% Oxygen, and 0.4% Carbon Dioxide, along with traces of other gases. Earth's main atmosphere ends at 100 kilometers (62 miles) above sea level. This point is known as the Karman Line.

Layers
The Earth has 5 main layers. The crust, which is the thinnest layer of Earth and causes continental drift. The upper and lower mantle, which has some lava and hot rock. The outer core, which is mostly hot iron. And the inner core, where Earth's magnetic field is generated.

Formation
Earth formed roughly 4.543 billion years ago, about 15 million years after the formation of Jupiter, Saturn, Uranus, and Neptune. Planetesimals merged together, and formed Earth.

Moons
Earth has one natural satellite, along with 2,000 man-made satellites in orbit. The ISS is the largest of Earth's man-made satellites, at 109 meters. Near-Earth Asteroids can be captured by Earth's gravity and orbit it for a temporary amount of time.