Volatile evolution on terrestrial planets

Introduction

Volatile elements, such as water, carbon, and nitrogen, with low condensation temperatures, are needed to achieve and sustain habitable conditions. They also regulate planets' geodynamics and climate evolution. However, how these volatiles were delivered to terrestrial planets and how they subsequently evolved is actively debated.

Importance of Noble Gases

Due to their inertness and high volatility, the noble gases krypton and xenon are unique geochemical tracers of volatiles. Their non-radiogenic isotopes have kept the signatures of the sources that delivered volatiles to planets and of the evolutionary processes subsequent to accretion, like recycling via subduction.

Analytical Challenges

Yet the non-radiogenic krypton and xenon isotopes have barely been used, in particular for krypton, due to major analytical challenges.

Proposed Development

Here, I propose to develop an original geochemical tool, the non-radiogenic krypton and xenon isotopes. I will develop innovative analytical protocols to allow high precision measurements of these isotopes.

Objectives

The objectives are to determine the source(s) of volatiles for terrestrial planets and to assess when volatiles started being recycled into the Earth’s mantle via subduction. To achieve these goals, I will:

1. Determine the precise krypton and xenon compositions of different types of meteorites to evaluate whether one meteorite type can explain the signature of the Earth’s and Mars’ mantles.
2. Assess the volatile source(s) of the Martian mantle by studying the krypton and xenon compositions of the Martian meteorites shergottites and nakhlites.
3. Determine the krypton and xenon compositions of different Earth’s mantle sources, from the present day to the Archean, by analyzing mid-ocean ridge basalts and granitoids.

Experimental Approach

The analyses on granitoids will be combined with high-pressure high-temperature experiments to study the krypton and xenon elemental fractionation processes, which will be key to providing a global understanding of the measured fluid compositions in granitoids.