FETA · Fluid impacts in EarTh Accretion
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2016-11-01 → 2018-10-31
- EU contribution
- €183,455
- Participants
- 1
- Scheme
- MSCA-IF-EF-RI
Lines connect the coordinator with its partners.
Results in brief
Fluid impacts in EarTh Accretion
Thanks to extinct radioactivity we know that the Earth formed 4.6 billion years ago by successive collisions between planetary objects. After each collision, the colliding objects merge and form a larger and larger planet. It took about 100 million years to form the fully-grown Earth with a metallic core overlaid by a rocky mantle. The large impacts that formed the Earth set the initial temperature and composition for the core and the mantle. They therefore determined the long-term evolution of our planet, including the initiation of plate tectonics, the generation of the geomagnetic field, the formation of oceans and atmospheres, and the development of life. Remote in space and time, Earth formation by large impacts is poorly understood and fundamental questions remain: How did the core and the mantle of the Earth form? What were their initial composition and temperature? Answering these questions was the main objective of this project. Much of what we know about Earth formation comes from geochemical observations. Isotopic data tell us about the timing of core and mantle differentiation. The composition of Earth's mantle constrains pressure and temperature. Following an impact, chemical species partition into the core and mantle. Therefore, in order to interpret the geochemical observations, we must know the efficiency of chemical transfers between the core and the mantle, which depends on physical processes. Unfortunately the physics of Earth differentiation by impacts had been little investigated. After each impact, prodigious amounts of energy were released, melting the impactor and the proto-Earth (figure 1). The metallic core of the impactor was then released into the Earth’s liquid mantle, called magma ocean. This process is highly turbulent: inertia is large compared to viscous forces. Turbulence generates small-scale mixing between the impactor core and the mantle silicates. Such mixing allows for chemical transfers between the two liquids. The specific objective of this project was to predict the efficiency of mixing and chemical transfers. This was key to deciphering the geochemical observations and understanding the origin of the Earth, planets, and exoplanets.
Data: CORDIS, © European Union
Project objective
Geochemical and geophysical observations indicate that much of Earth’s mass was accreted during large impacts between planetary embryos already differentiated into a metallic core and a silicate mantle. These collisions played a crucial role in setting the stage for Earth evolution, including the initiation of plate tectonics, the generation of Earth’s magnetic field, and the development of life. Each impact delivered prodigious amounts of energy, melting the projectile and the protoplanet's mantle, and creating an environment where the metallic liquid core of the projectile was released within a molten silicate magma ocean. The fate of the projectile’s core following impact affected the efficiency of chemical equilibration between metal and silicates, and therefore the geochemistry of Earth’s deep interior. Recent studies have provided clues on the physical processes involved, however, major questions remain. For instance, does the projectile’s core remain coherent or does it fragment into drops during the impact ? This project includes the first analog fluid mechanics experiments on large impacts that formed the Earth, and combines them with numerical simulations and theory. Complementary to simulations, experiments can produce turbulence, as expected during Earth accretion. Regime diagrams and scaling laws on turbulent mixing obtained from these experiments and simulations will provide key constraints to interpret geochemical observations in terms of accretion time scales and processes. Bridging gaps between fluid mechanics, geodynamics, impact cratering and geochemistry, this project is expected to bring fundamental progress in our understanding of the origin of the Earth, planets, and exoplanets. The researcher’s expertise in Earth accretion and in lab experiments, acquired in the USA, will be reinvested in Europe through this project. Because the work is in fluid mechanics, the host organisation is the ideal place for this project.
Original text from CORDIS.
Participants
- THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE · CAMBRIDGECoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union