Earth's missing elements were lost in violent collisions during formation

Planetary formation has always fascinated scientists. Understanding how Earth and Mars formed, and why they contain fewer essential elements than expected, remains one of the biggest mysteries in planetary science.

The chemical composition of planets plays a crucial role in shaping their ability to support life. Some elements, such as copper and zinc, help regulate planetary chemistry and often accompany water, carbon, and nitrogen – the building blocks of life.

Elements on Mars and Earth

For years, researchers believed that Earth and Mars started out with fewer of these moderately volatile elements (MVEs).

The prevailing idea was that these elements either failed to condense in the early solar system or were lost during the process of planetary formation.

However, a new study published in Science Advances challenges this long-standing assumption.

Led by Assistant Professor Damanveer Grewal from Arizona State University, in collaboration with researchers from Caltech, Rice University, and MIT, the study takes a fresh approach to understanding how planets acquired their chemical constituents.

A new approach to an old mystery

The research team turned to iron meteorites – remnants of the metallic cores of ancient planetesimals. These small, celestial bodies were the first building blocks of planets.

By studying their chemical composition, scientists hoped to uncover clues about how Earth and Mars formed.

Their findings were unexpected. Many of these early planetesimals were surprisingly rich in MVEs. This contradicts earlier theories suggesting that these elements never made it into planetary bodies in the first place.

Instead, the study suggests that Earth and Mars initially had plenty of these elements but lost them later through a different process.

“We found conclusive evidence that first-generation planetesimals in the inner solar system were unexpectedly rich in these elements,” said Grewal. “This discovery reshapes our understanding of how planets acquired their ingredients.”

Role of violent collisions

If these essential elements were present in the early building blocks of Earth and Mars, why are they missing today?

The answer, according to the study, lies in a chaotic period of planetary growth. During this time, massive collisions reshaped young planets, stripping away many of their original components.

Previous theories focused on two possible explanations for the missing MVEs. One suggested that these elements never fully condensed in the solar nebula, meaning that they were never available for planets to collect.

The other proposed that they were lost when planetesimals underwent differentiation, a process in which heavy materials sink to form a core while lighter materials rise. However, the new study presents a different explanation.

Surprisingly, many inner solar system planetesimals preserved their original MVE levels. This suggests that the depletion of these elements did not happen in the earliest stages of planetary formation.

Instead, Earth and Mars likely lost their MVEs over time as they experienced powerful impacts and mergers with other celestial bodies.

Understanding planetary formation

“Our work redefines how we understand the chemical evolution of planets,” Grewal explained. “It shows that the building blocks of Earth and Mars were originally rich in these life-essential elements, but intense collisions during planetary growth caused their depletion.”

This finding changes how scientists view planetary chemistry. Instead of assuming that Earth and Mars were always missing MVEs, the study suggests that they were lost gradually due to cosmic impacts.

This insight could help researchers refine models of planetary formation, offering a clearer picture of how Earth became the habitable world it is today.

Why does any of this matter?

Beyond reshaping theories about the formation of Earth and Mars, this research has broader implications for understanding other planets.

If violent collisions played a major role in determining the chemical makeup of planets, then similar processes may have shaped other worlds as well.

Planets in different solar systems may have started with similar elemental compositions, only to lose or retain certain elements depending on their history of collisions.

This means that studying exoplanets – planets outside our solar system – could provide further clues about how common these processes are.

The study also raises new questions. If Earth lost MVEs due to collisions, how did it still manage to retain enough essential ingredients for life?

Did certain planetary conditions help preserve water, carbon, and nitrogen while allowing MVEs to escape?

These are questions that scientists will continue exploring in future research.

Earth’s missing elements and the future

This study marks an important step in understanding planetary chemistry. It challenges old assumptions and offers a new way to think about how planets form and evolve.

By analyzing ancient meteorites, researchers have revealed a history of planetary growth shaped by violent events rather than simple elemental scarcity.

The mystery of Earth’s missing elements may not be fully solved yet, but this research adds a new piece to the puzzle – one that could change how we view planetary evolution forever.

The study is published in the journal Science Advances.

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