New insights into Earth's iron core could change when and how scientists believe it was formed.
Huge collisions between the developing Earth and other objects were believed to have generated significant amounts of iron vapor, Lawrence Livermoore National Laboratory reported. The results of a recent study reveal that iron vaporizes easily during these events, potentially changing the way researchers look at the formation of our solar system.
"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 is mixed. This new information actually changes our estimates for the timing of when Earth's core was formed," said LLNL scientist Richard Kraus.
Planets are believed to form through a series of impacts, which become faster (reaching up to 100,000 miles per hour) and more intense as the objects grow larger. Scientists still don't have very accurate models for what occur in these final stages of formation, when temperatures and pressure are staggeringly high.
"One major problem is how we model iron during impact events, as it is a major component of planets and its behavior is critical to how we understand planet formation," Kraus said. "In particular, it is the fraction of that iron that is vaporized on impact that is not well understood."
A team of researchers used Sandia National Laboratory's Z-Machine to develop a new shock-wave technique that can measure entropy gain during shock compression. This measurement revealed what conditions would be necessary in order for the early Earth's iron to be vaporized. The scientists determined iron can be vaporized at much lower impact speeds than was previously believed, and there was more iron being vaporized during Earth's early days.
"This causes a shift in how we think about processes like the formation of Earth's iron core. Rather than the iron in the colliding objects sinking down directly to the Earth's growing core, the iron is vaporized and spread over the surface within a vapor plume. After cooling, the vapor would have condensed into an iron rain that mixed into the Earth's still-molten mantle," Kraus said.
The findings were published in a recent edition of the journal Nature Geoscience.
