Earth and Mars followed different formation pathways, study finds

Researchers from the University of Copenhagen’s Center for Star and Planet Formation have concluded that Earth and Mars followed distinct formation pathways during the early development of the solar system approximately 4.56 billion years ago. The study, published in Nature Astronomy, suggests that both pebble accretion and planetesimal collisions played roles in planetary growth, but in vastly different proportions.

According to the findings, at least 75 percent of Earth’s mass originated from two young protoplanets that grew by sweeping up drifting pebbles, with planetesimal collisions contributing up to 25 percent. In contrast, Mars formed primarily through the impact of massive planetesimals, which accounted for roughly 73 percent of its mass, while pebble accretion contributed only about 27 percent.

To reach these conclusions, the research team analyzed chemical signatures in planetary crusts and mantles, specifically focusing on the depletion of moderately volatile elements such as sodium, zinc, potassium, lithium, and manganese. These chemical fingerprints provide evidence of how the planets accumulated their initial mass and help explain the distinct internal structures and volatile inventories of these two terrestrial worlds.