Hadean facts for kids

Artist's impression of a Hadean landscape.

Imagine Earth as a fiery, chaotic place, constantly hit by space rocks. That's what the Hadean eon was like! It's the very first period in Earth's long history. This incredible time began when our planet first formed, about 4.6 billion years ago. It ended around 4 billion years ago.

The name "Hadean" comes from "Hades." In ancient Greek stories, Hades was the god of the Underworld. This name fits perfectly because Earth was incredibly hot and wild back then. A geologist named Preston Cloud first used this term in 1972. During the Hadean, our young Earth was constantly hit by meteors. There were also many volcanoes erupting everywhere.

Scientists haven't found any regular rocks from the Hadean eon. This is because the Earth was still forming and changing so much. However, they have found tiny, super-tough crystals called zircons. These zircons are like tiny time capsules. Some are as old as 4.4 billion years! It's amazing that anything survived from such a violent time.

It's believed that Earth was mostly molten, like melted rock, for a very long time. This was due to all the impacts and intense heat. But as things slowly cooled, water vapor would have started to form. Eventually, the first oceans would have appeared.

How the Moon Was Born

One of the most exciting things that happened during the Hadean was the birth of our Moon! Scientists believe a huge collision created it. Early in Earth's history, a giant object, perhaps as big as Mars, crashed into our planet. This massive impact threw a huge amount of material into space. Over time, this material clumped together to form the Moon.

Scientists have strong evidence for this "giant impact hypothesis":

1. The rocks from the Moon are very similar to rocks from Earth's outer layer.
2. The Moon's center has very little iron. This suggests it formed from Earth's outer layers, not its core.
3. The way Earth and the Moon spin together is unique. It matches what would happen after such a huge crash.

A Time of Constant Impacts

Why are there so few rocks left from the Hadean eon? The early Solar System was a very messy place! After the planets formed, there were still many leftover space rocks. These included small planets, asteroids, and comets. They flew around our Solar System in wild paths.

These space objects constantly crashed into Earth and other planets. This period of heavy impacts lasted until about 3.8 billion years ago. It was like a cosmic shooting gallery! This constant bombardment might have stopped large pieces of Earth's crust from forming. It literally shattered any early landmasses.

The most intense part of this era was called the Late Heavy Bombardment. During this time, Earth and the Moon were hit by a huge number of very large objects. You can still see the craters from these impacts on the Moon today!

Early Earth's Atmosphere

No life forms are known from the Hadean eon. The conditions were simply too extreme. The early atmosphere was very different from today's air. It contained gases like carbon dioxide, methane, and nitrogen. But there was almost no oxygen. This means no animals or plants as we know them could have survived. Life would only begin to appear much later, in the Archaean eon.

Images for kids

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  Backscatter electron micrograph of tiny zircon crystals from Australia. These are some of the oldest known pieces of Earth.

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  Artist's impression of Earth and Moon towards the end of the Hadean. You can see the first water vapor clouds and oceans appearing on Earth.

See also

In Spanish: Eón hádico para niños