Researchers Determined Earth and Mars Formed Differently
A new study reveals that Earth and Mars accreted mass through distinct building block processes 4.5 billion years ago.
Updated on Oct. 2, 2026 in Geology
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A study published on October 2, 2026, found that Earth and Mars formed 4.5 billion years ago via different accretion mechanisms within the same gas and dust cloud. While Earth primarily grew through protoplanets, Mars acquired most of its mass from smaller building blocks called planetesimals.
Why it matters
Understanding how planetary mantles retain chemical imprints of their formation is essential for deciphering the early history of the solar system. This study provides a refined hybrid model explaining how different proportions of pebbles and planetesimals created terrestrial planets.
Researchers used computer models to analyze volatile elements including sodium, zinc, and potassium in the planetary mantles. The data indicates at least 75 percent of Earth's mass came from pebble accretion, while Mars derived 75 percent from planetesimals.
The players
University of Copenhagen
This is a premier research institution that hosted the scientists responsible for conducting the geochemical modeling in this study.
Nature Astronomy
This is a peer-reviewed scientific journal that publishes high-impact research regarding space and planetary sciences.
The details
The study suggests that although both planets emerged from a single cloud of gas and dust, they followed diverging evolutionary paths. By mapping the chemical signatures of volatile elements, scientists confirmed that planetesimals—solid kilometer-sized objects—played a much larger role in the formation of Mars than in the formation of Earth.
Timeline
Earth and Mars formed 4.5 billion years ago.
Study results were published on October 2, 2026.
The Big Picture
The study updates the hybrid model of planet formation by demonstrating that terrestrial planets can possess vastly different internal histories despite sharing a common solar origin. This research shifts the focus toward individual accretion pathways rather than assuming a universal growth pattern for all rocky planets.
While this study focuses on ancient planetary formation, the refined modeling techniques improve our ability to analyze the composition of exoplanets in other solar systems. These chemical fingerprinting methods may eventually help identify which distant planets possess the necessary volatile elements to support life.
The takeaway
This discovery highlights that even planets that appear similar in our solar system can be composed of fundamentally different building materials. Future space exploration missions may use these findings to better interpret soil and rock samples collected from other planetary bodies.
Further reading
Learn more about planetary evolution and crustal history in the Geology section.
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Does understanding the origins of other planets change how you view humanity's place in the universe?
