Iron, one of the most abundant elements on Earth, helped give rise to entire civilizations and is the key ingredient in steel, without which many of our modern structures would not be standing. The story of iron's origins is astronomical, with the element being born from the explosion of stars.

Supernova
By scientific standards, the formation of iron is one of the most violent processes imaginable. A type of star known as a red giant begins to turn all of its helium into carbon and oxygen atoms. Those atoms then begin to turn into iron atoms, the heaviest type of atom star can produce. When most of a star's atoms become iron atoms, the star becomes what is known as a supernova. It explodes, showering space with iron, oxygen and carbon atoms far and wide.

From here, gravity takes over, forming the atoms into planets such as Earth.

Earth's Main Building Block
Born of these violent explosions, Earth's core is likely mostly molten iron, and its crust is estimated to be about 10 percent iron. The life on Earth also contains iron, from plants to humans. The abundant metal is truly one of Earth's essential building blocks.

Iron From Meteorites
Not all iron on the Earth's surface got here with its initial planetary formation. Massive chunks of rock known as asteroids have broken apart throughout the history of our solar system, sometimes through collisions with other asteroids, showering down smaller chunks of rock. The meteorite fragments that came into Earth's atmosphere, and did not burn up in the intense heat, brought more iron to the planet's surface.

Iron and Mankind
Though it has been an essential part of Earth since the planet's inception, humans did not begin producing iron into usable implements and products until about 2000 B.C. The historic period known as the Iron Age began in south-central Asia, replacing what had been the key metal, bronze. Civilizations learned that iron, when mixed with carbon, is more durable than bronze. Iron weapons also hold a sharper edge.

Ancestor of Steel
Iron continued as the key metal fabric in human civilization until the 1850s, when innovators began to learn that if a bit more carbon was added to iron during the production process, a durable yet flexible metal resulted. By the 1870s, production innovations would make this new metal alloy called steel more economically viable to mass produce. The demand for steel skyrocketed during the railroad boom of the 1800s, as the metal made an ideal material for rail production.