New insights into the history of Earth’s atmosphere through neon and xenon isotopes.

Tracking changes in the composition of the Earth’s atmosphere over geological time allows us to trace the history of our planet and the processes that have shaped it over more than 4 billion years. Two major mechanisms remain poorly understood for the earliest periods: mantle degassing and atmospheric escape into space.

In a study published in the journal Science Advances, a team of researchers from the Institut de Physique du Globe de Paris (Université Paris Cité, CNRS) and Washington University in St. Louis (United States) analyzed the isotopic and elemental composition of rare gases (neon, argon, krypton, and xenon) trapped in fluid inclusions of very ancient hydrothermal quartz from the Barberton greenstone belt (3.3 billion years old, South Africa) and the Fortescue Group (2.7 billion years old, Australia). These inclusions are veritable time capsules, recording the composition of the atmosphere at the time of their formation.

The results show that the isotopic ratio of neon (²⁰Ne/²²Ne) was slightly lower in the primitive atmosphere, reflecting intense mantle activity and significant degassing of solar neon during the first billion years of Earth’s history. Furthermore, the Archean atmosphere contained about twice as much xenon as today, confirming a gradual escape of xenon into space and thus a depletion of this gas over time. 

These observations provide new constraints on the physical and chemical processes that shaped the Earth’s atmosphere and shed light on major transitions, such as the Great Oxidation Event.These observations provide new constraints on the physical and chemical processes that shaped Earth’s atmosphere and shed light on major transitions, such as the Great Oxidation Event 2.3 billion years ago, when oxygen began to accumulate in the air.

Link  to the article : https://www.science.org/doi/10.1126/sciadv.aea3380