Published : 03 Oct 2026, 10:02 PM
Updated : 03 Oct 2026, 10:02 PM
Earth and Mars formed in different ways despite emerging from the same rotating cloud of gas and dust that eventually became the solar system, researchers have found.
The findings, reported by The Economic Times, come from a study published in Nature Astronomy that reconstructs the earliest stages of the two planets’ formation 4.5 billion years ago.
“The most surprising result was that Earth and Mars appear to have formed in different ways,” said Anders Johansen, a study author and co-lead researcher at the Globe Institute, University of Copenhagen.
The researchers had expected two planets formed side by side in the same solar system to have more similar formation histories.
Co-lead researcher Haiyang Wang, an assistant professor at the Globe Institute, said at least 75 percent of Earth’s mass appears to have come from two young planets known as protoplanets, which grew by accreting pebbles. Planetesimals contributed up to 25 percent.
Protoplanets and planetesimals are both planetary building blocks, but they differ in size. Planetesimals are solid, kilometre-sized bodies formed from cosmic dust, while protoplanets are larger, ranging from moon-sized to Mars-sized planetary embryos.
In contrast, roughly three-quarters of Mars’ mass appears to have come from planetesimals, with the remaining quarter originating from pebble accretion, Wang said.
The study examines how the two planets formed by analysing specific elements in their crusts and mantles.
Scientists broadly agree that planets form primarily through one of two processes, or a combination of both. One involves collisions between giant space rocks known as planetesimals, while the other sees larger bodies accumulate smaller particles through pebble accretion.
Planetary scientists have yet to settle on which process, or combination, best explains the formation of rocky planets such as Earth and Mars.
The researchers said their findings support the hybrid model while offering a more specific account of how the two planets formed 4.5 billion years ago.
They focused on volatile elements such as sodium, zinc and potassium, which evaporate relatively easily at high temperatures.
According to the researchers, the presence or absence of these elements acts as a chemical fingerprint of the processes that planets underwent during formation.
Using computer models, the researchers can then assess which formation scenarios best explain the origins of Earth and Mars, The Economic Times reported.
“It is a major detective job to figure out what happened back then when most of the evidence disappeared long ago,” Johansen said.
Even after 4.5 billion years, he added, the compositions of Earth’s and Mars’ mantles remain unchanged and can be viewed as an imprint of their formation processes.
