Chemistry of the Earth's Earliest Atmosphere

TL;DR

This paper reviews the chemical composition and evolution of Earth's earliest atmosphere, emphasizing its secondary origin, sources of volatiles, and the chemical processes during Earth's accretion and early atmospheric stages.

Contribution

It provides a comprehensive synthesis of current understanding of early Earth's atmospheric chemistry and discusses unresolved questions in the field.

Findings

Earth's atmosphere likely originated from outgassing rather than solar nebula capture.

Meteorites serve as analogs for Earth's initial volatile sources.

Chemical processes during accretion shaped the early atmospheric composition.

Abstract

In this chapter we describe chemistry of the early atmosphere of the Earth during and shortly after its formation where there is little if any geological record. We review the arguments for a secondary origin of the terrestrial atmosphere, that is by outgassing during and/or after accretion rather than by capture of solar nebula gas. Then we discuss sources of volatiles accreted by the Earth using meteorites as analogs for the material present in the solar nebula. The next section reviews heating during accretion of the Earth. Subsequently we describe chemistry of the silicate vapor, steam, and gaseous stages of atmospheric evolution on the early Earth. We close with a summary of the key questions that remain unresolved.