The Hadean Eon is a geologic event that occurred around 4.5 billion years ago when the Earth began to form. At first there was just a cloud of gas and dust, and then the Sun Formed, an gradually the planets formed.

Why is it called the Hadean Eon?

The Hadean Eon is named by scientists after the Greek god Hades who ruled the underworld. That's because during most of the Hadean period, the surface of the Earth must have been the Christian image of Hell.

What happened in the Hadean Eon?

Around 45 Million years after the Earth was formed, a large planetoid about the size of Mars, crashed into Earth. Little bits of hot rocks splashed off during the crash and orbited around the Earth. Eventually this bits joined together, cooled off, and became the Moon.

On Earth, and probably other planets too, the heavier iron atoms sank down and became the core of the Earth, and lighter atoms like silica and hydrogen rose to the surface. Most of gases such as hydrogen, carbon dioxide, methane, ammonia, and nitrogen floated away into space. Water, brought to Earth by comets that crashed into Earth, boiled into steam because the Earth was still very hot. The water formed a steam atmosphere around the Earth.

The oldest rocks formed

Around 4.4 billion years ago, most of the planetoids have gotten smashed up into dust or had become part of a bigger planet. There weren't any more of them to smash into earth.

Now that planetoids weren't always amashing into them, the Earth and the Moon formed rocky crusts of silica all over them. The oldest Earth rocks and Moon rocks we know about both date to this time. These are igneous rocks like granite and quartz.

 The oceans fromed

As the Earth cooled down, about 4.3 billion years ago, the steam in the atmosphere also cooled down and fell as rain on Earth and then oceans were formed on the surface of the Earth. By 4.2 billion years ago, Earth had lan and oceans just as it does today. Tectonic plates may have been moving the land and oceans around.

The first steps towards living creatures

In some parts of the Earth, the oceans may have been frozen into ice, as the North and South Poles are today. Inside the oceans, amino acids from space began to join together into the first proteins - not yet life but a step along the way. Probably the earliest RNA also formed at this time.

By now a billion years have passed. By about 3.5 billion years ago, the continents were beginning to form on Earth. This marks the change to the next eon, the Archean.