The Hadean Eon

The Hadean Eon

The Hadean Eon

4.6 - 4 billion years ago

Other interesting facts

What was the world like?

Major events

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Hadean climate

Hadean organisms

There is no evidence for life of any sort existing during the Hadean eon. Conditions were simply too harsh, to the point where is life had formed during this period, it would have died out too quickly to have made any meaningful impact.

During the Hadean eon, Earth's climate was incredibly harsh. The planet's temperature was very intense, and impacts from extraterrestrial objects were common. Much of the planet consisted of molten seas, although a solid crust began to form as the eon came to a close.

Hadean atmosphere

The Earth's atmosphere at this time was very different. The ozone layer had not formed, meaning the Earth was unprotected from solar radiation, which contributed to the intense temperatures. Additionally, there was a notable lack of free atmospheric oxygen and an abundance of sulfur isotopes.

Artist's conception of Hadean Earth, taken from the Weather Channel

Formation of the Earth and Moon

The process by which the Moon was formed has been highly debated. However, consensus posits that a collision between the Earth and an object roughly the size of Mars resulted in the ejection of material that eventually coalesced into the Moon. However, further study has found that the Moon may actually be the result of many collisions of smaller objects with the Earth.

This eon began with the formation of the Earth. Based on the leading hypothesis, the Earth formed from the slow accretion of dust and gas in space, and was helped along by frequent collisions with smaller planetesimals. Once the Earth was fully formed it had a molten surface, and objects continued to collide with the Earth. Eventually, the surface and core of the Earth began to stabilize.

Additional facts:

• This point of geologic time has no official subdivisions, since there are very few geological traces from this eon.
• There are however informal divisions based on the Lunar geologic time scale.
• Comet impacts may have brought ice to this molten Earth, which would have become water vapor and then precipitation, leading to the presence of liquid water on the surface.
• The minerals of this eon are poorly preserved in the known rock record, forcing scientists to study what minerals could plausibly have existed at the time.
• The frequent asteroid and comet impacts likely also impacted (get it?) the mineral diversity of the eon.
• Other proposed models of Hadean Earth include one that was predominantly water and one that was periodically ice-covered. In these scenarios, lightning from volcanic ash clouds may have resulted in early life forming.