Not From Deep Space: New Study Reveals Where Earth Was Truly Born

Hyderabad: Planetary scientists from ETH Zurich have made a significant discovery regarding the formation of Earth. As opposed to the earlier belief that a good chunk of material that formed our planet came from the outer Solar System (beyond Jupiter), the new study suggests otherwise, claiming that the material came exclusively from the inner Solar System.

Using a new analysis of existing data, scientists found that the material that formed Earth is similar to that found on Mars and the asteroid Vesta, suggesting that Earth is indeed a part of a trend line extending from the Sun. This close relationship would also allow researchers to make predictions about the composition of Venus and Mercury, from which we have no known samples.

Isotope signature reveals origin of Earth

The new discovery depends on the study of isotopes, which are sibling atoms of the same element with a different mass. In other words, isotopes carry the same number of protons but have a different number of neutrons. For their research, Paolo Sossi and Dan Bower, from ETH Zurich, compared isotopic ratios of a wide range of meteorites, including those from Mars and the asteroid Vesta, with those of Earth.

This is roughly what the formation of the Earth in our solar system might have looked like. The birth of two planets (light brown dots) in a protoplanetary disc around the young star WISPIT 2. (Image Credits: ESO / Lawlor C et al.)

While previous studies mostly considered only two isotopic systems, ETH researchers used existing data on ten different isotopic systems from meteorites and analysed them using a specialised statistical method. The new study, published in the journal Nature Astronomy, concludes that material from the outer Solar System is likely to account for less than two per cent of Earth’s mass, or even nothing at all.

“Our calculations make it clear: the building material of the Earth originates from a single material reservoir," says Paolo Sossi from ETH Zurich. His colleague Dan 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.”

Earth is made up of non-carbonaceous meteorites

Researchers have long used isotopes in meteorites to trace their origins within the Solar System. Initially, only oxygen isotopes were useful, but since the early 2010s, chromium and titanium isotopes have allowed scientists to distinguish between two groups:

• Non-carbonaceous meteorites: formed in the inner Solar System.
• Carbonaceous meteorites: richer in water and carbon, originating in the outer Solar System.

Early formation of Jupiter likely blocked outer Solar System material from reaching Earth. (Image Credits: NASA)

Recent analysis shows Earth is made entirely of non-carbonaceous material, meaning it formed in the inner Solar System without mixing from the outer regions. This suggests Earth grew by incorporating nearby planets in a relatively stable environment, and that volatile elements like water were already present in the inner Solar System.

Jupiter has a role to play

Researchers believe the Solar System split into two distinct material reservoirs because Jupiter’s rapid growth created a gravitational barrier in the protoplanetary disc, preventing outer Solar System material from mixing with the inner region. New analysis shows almost no material from beyond Jupiter reached Earth, confirming Earth’s composition is similar to Vesta and Mars.

The study also suggests Venus and Mercury likely share this same composition, though this cannot yet be verified due to the absence of rock samples from those planets.