New research suggests unique geochemical signatures found in iron-rich meteorites were produced by a process called core crystallization inside the solar system's oldest planetary objects, according to a study published in the journal Nature Geoscience.

For nearly as long as scientists have been finding meteorites, they've been working to group and classify them based on their mineralogy.

As instrumentation and chemical analysis techniques have gotten more sophisticated, scientists have been able to organize meteorites into even smaller groups.

"We found that iron meteorites on Earth represent the early crystallized portion of planetary cores, which is low in sulfur and enriched in the heavy isotopes of iron," study lead researcher Peng Ni, research fellow at the Carnegie Institution for science, told UPI.

For decades, scientists have been examining the relationships among iron-rich meteorites, which are distinct from rocky meteorites in both appearance and chemical composition.

But scientists have only recently begun using isotopic analysis to more precisely classify iron-rich meteorites.

Most elements can be found in a variety of forms, or isotopes. Elements typically have a stable number of protons, but different isotopes possess different numbers of neutrons.

Scientists have previously used the ratios of oxygen isotopes to trace disparate meteorites -- fragments separated by thousands of years and as many miles -- to the same parental bodies.

For the new study, researchers examined ratios of iron isotopes in these same meteorites to better understand the geochemical processes happening inside primordial bodies.

Because different processes favor some isotopes over others, isotope ratios can be used to better understand how meteorites came to possess specific geochemical signatures.

"Scientists found that iron meteorites are enriched in the heavy isotopes of iron" that match the "initial chemical composition of their parent bodies," Ni said.

"The discovery of these signatures requires precise measurements of iron isotopic ratios down to differences of less than 1/10000th, which was not technically possible until less than 20 years ago," Ni said.

Scientists have previously identified these unique iron isotopic ratios, but were unable to explain their origins. Through a series of lab experiments, Ni and his colleagues were able to show that such isotopic ratios are best explained by an internal process called core crystallization.

Researchers replicated the core crystallization process in the lab and found that they could produce mineralization patterns and isotopic ratios similar to those found in iron-rich meteorites.

"We further confirmed our findings by conducting sophisticated modeling to predict the evolution of iron isotopic composition, and concentrations of other elements, such as gold and iridium, during core crystallization, which matches the chemical trends observed in iron meteorites," Ni said.

Researchers suggest their findings can help scientists better understand the planetary evolution in the early solar system. The findings could also guide the science of future NASA missions.

"For example, a NASA mission named Psyche, scheduled to launch in 2022, will bring us to a unique metal asteroid in the asteroid belt, which is potentially the exposed core of an early planet," Ni said.

"If so, our research would help predict the composition of different parts of the planet and aid in the planning of future sample return," he said.

Related Links
Explore The Early Earth at TerraDaily.com

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