Collision fueled iron vapors give clues to formation of Earth's core

A new study has provided a deeper insight into how iron vapors are associated with the formation of Earth's core.

According to a new study by LLNL scientist Richard Kraus and colleagues, violent collisions between the growing Earth and other objects in the solar system generated significant amounts of iron vapor.

The results showed that iron vaporizes easily during impact events, which forces planetary scientists to change how they think about the growth of planets and evolution of our solar system.

For planetary scientists, one of the most important and complex research areas was predicting how planets form and evolve to their current state. Generally speaking, planets form by a series of impacts, with the speed of the impacts being slow at first, a few miles per hour, but then faster as the planets grow larger, up to 100,000 miles per hour.

At the end stages of formation, when the impact speeds are high and the material conditions are extreme (high temperatures and pressures), planetary scientists don't have great models for how to describe what happens to the colliding bodies.

The Sandia Z Machine was used to develop a new shock-wave technique to measure an important material property.

Using Sandia National Laboratory's Z-Machine, the team developed a new shock-wave technique to measure an important material property, the entropy gain during shock compression. By measuring the entropy, they determined the critical impact conditions needed to vaporize the iron within objects that collide with the growing Earth.

The scientists found that iron will vaporize at significantly lower impact speeds than previously thought. This translates to more iron being vaporized during Earth's period of formation.

Kraus said that rather than the iron in the colliding objects sinking down directly to the Earth's growing core, the iron was vaporized and spread over the surface within a vapor plume and after cooling, the vapor would have condensed into an iron rain that mixed into the Earth's still-molten mantle.

The timing of Earth's core formation can only be determined via chemical signatures in Earth's mantle, a technique that requires assumptions about how well the iron was mixed and this new information actually changes the estimates for the timing of when Earth's core was formed, he further added.