Hadean Eon

The Earth's origins, before the advent of life

The Hadean is the earliest eon in Earth's history; it occurs before the Archean Eon.

There are no formal subdivisions in the Hadean
The Hadean Eon is divided (informally) into 4 periods
- Cryptic; Basin Groups; Nectarian; Early Imbrian

The Hadean is not officially recognized by the International Commission on Stratigraphy, since no actual strata from this period now exist.
Marked by the formation of the solar system and the Earth
- Formation of the rocky Earth out of collisions of planetoids
- Formation of the Earth's crust
  - None of Earth's early surface survive from this time
Cosmic bombardments from comets and planetoids
- In the cosmic stage, a still-forming Earth and our solar system took a daily pounding from rocky asteroids and icy comets between 4.1 to 3.8 billion years ago and brought the basic building blocks of life that could be concentrated and polymerized in the crater basins (Chatterjee 2013)
Primal oceans with organic substrates
Reducing atmosphere: oxidation is prevented by the lack of oxygen and other oxidizing gases.
The origin of life (abiogenesis) might be possible during this time, but stronger evidence is needed.
- Evidence from a single zircon (out of 10,000) exhibited graphite inclusions (Bell et al. 2015)
- 12C-rich isotopic signature may be evidence for the origin of life on Earth by 4.1 Ga.
- Confirmatory evidence will be needed to show that this graphite was not contamination.