Why there are three different layers of iron in solar system?

According to a new study, Carnegie's Stephen Elardo and Anat Shahar shows that interactions between iron and nickel under the extreme pressures and temperatures similar to a planetary interior can help scientists understand the period in our Solar System's youth when planets were forming and their cores were created.

The findings are published in journal Nature Geoscience.

Earth and other rocky planets formed as the matter surrounding our young Sun slowly accreted. At some point in Earth's earliest years, its core formed through a process called differentiation--when the denser materials, like iron, sunk inward toward the center. This formed the layered composition the planet has today, with an iron core and a silicate upper mantle and crust.

One of the key to research Earth's differentiation period is studying variations in iron isotopes in samples of ancient rocks and minerals from Earth, as well as from the Moon, and other planets or planetary bodies.

Every element contains a unique and fixed number of protons, but the number of neutrons in an atom can vary. Each variation is a different isotope. As a result of this difference in neutrons, isotopes have slightly different masses.

One outstanding mystery on this front has been the significant variation between iron isotope ratios found in samples of hardened lava that erupted from Earth's upper mantle and samples from primitive meteorites, asteroids, the Moon, and Mars.

"There's still a lot to learn about the geochemical evolution of planets. But laboratory experiments allow us to probe to depths we can't reach and understand how planetary interiors formed and changed through time," Elardo said.

Elardo and Shahar were able to use laboratory tools to mimic the conditions found deep inside the Earth and other planets in order to determine why iron isotopic ratios can vary under different planetary formation conditions.

They found that nickel is the key to unlocking the mystery.