A new analysis of meteorite isotopes challenges long-held ideas about Earth’s origins, suggesting our planet may have formed almost entirely from nearby material rather than distant sources.
Planetary scientists have long debated the origin of the material that formed Earth. Although our planet sits in the inner Solar System, many researchers have estimated that between 6 and 40 percent of its building material came from beyond Jupiter in the outer Solar System.
For years, scientists believed that outer Solar System material was needed to deliver volatile substances such as water. This idea implied that material must have moved between the outer and inner regions while Earth was forming. But new research is now questioning that assumption.
“We were truly astonished”
Paolo Sossi and Dan Bower of ETH Zurich compared isotopic data from a wide range of meteorites, including samples linked to Mars and the asteroid Vesta, with Earth’s composition. Isotopes are atoms of the same element that share the same number of protons but differ in mass because they contain different numbers of neutrons.
Using a new analytical approach, the team reached an unexpected conclusion. Earth appears to have formed entirely from material that originated in the inner Solar System.
Material from beyond Jupiter likely makes up less than 2 percent of Earth’s mass, and may not have contributed at all. The findings were published in Nature Astronomy.
“Our calculations make it clear: the building material of the Earth originates from a single material reservoir,” says Sossi. His colleague Bower adds: “We were truly astonished to find that the Earth is composed entirely of material from the inner Solar System distinct from any combination of existing meteorites.”
To reach this result, the researchers analyzed data from ten different isotopic systems found in meteorites and applied a statistical method not commonly used in geochemistry. Earlier studies typically relied on only two isotopic systems.
“Our studies are actually data science experiments,” says Sossi. “We carried out statistical calculations that are rarely used in geochemistry, even though they are a powerful tool.”
