Projets

Atmospheric geology

Atmospheric Geology: using atmospheric chemistry to constrain the geology of exoplanets


Luca Caricchi, Maria Ovtcharova, Urs Schaltegger (Department of Earth Sciences, UniGE), Nicolas Greber (Museum of Natural History, Geneva)

 

The secular cooling and the geological evolution of the Earth are intertwined with the composition of its atmosphere and its habitability. Magmatism and volcanism produced continents and were responsible for the formation of the oceans. Volcanic gas emissions and the interaction between water, atmosphere and surface rocks shaped the atmosphere’s chemistry over the Earth’s history. The composition of the atmosphere has changed dramatically over 4.5 Ga in concert with major geological events such as the onset of plate tectonics. The chemistry of volcanic gas emissions is intimately linked to the geotectonic setting and thus must also have been changing over Earth’s history but no quantitative data exist. This prevents any potential link to be established between the evolution of volcanic gas emissions and the chemistry of the atmosphere. We will submit an FNS standard grant in October 2021 for one postdoctoral researcher and two PhD students to trace the chemical evolution of the Earth’s crust and the chemistry of volcanic gas emissions over 4.5 billion years using the geochemistry of zircons and apatites included in them. Zircon can be dated thanks to its content of radioactive elements, its Zr and Si isotopic signature provide information on the evolution of the Earth’s crust and it protects its inclusions from modification associated with geological processes. Apatite is a perfect repository for volatiles dissolved in magmas (Cl, F, S, CO2, H2O) and allows volcanic gas emission to be quantified. Tracing the chemistry of volcanic gas emissions and surface rocks over Earth’s history will make our planet a Rosetta Stone to interpret the geology of exoplanets from the study of their atmosphere.

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