Abstract

The first 500 million years of the solar system were a decisive time for the geological evolution of the Earth into the planet we know today and how it became a habitable place. Understanding the chemical and physical processes by which the Earth formed is of central interest to not only Earth and planetary sciences. These processes ultimately delivered water and the essential organic compounds to Earth from which life originated and are, therefore, key to the environmental and biological evolution of our planet.

During this formation period, segregation of the Earth’s core depleted the silicate part of the Earth in elements that have a high affinity for metal phases, so-called siderophile elements, like the precious metals. According to this model, the Earth’s mantle and crust should be devoid of any of these elements, which is at odds with the fact that they are present in the silicate Earth at surprisingly high abundances. Here I will explore, to what extent a protracted meteorite bombardment replenished the siderophile element content of the Earth’s mantle during this ‘late veneer’ epoch more than 3.9 billion years ago.

Willbold, M, Elliott, TR & Moorbath, S. ‘The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment’, Nature, 477, (pp. 195-198), 2011