Earth and Mars Formed Through Different Planetary Processes

Earth and Mars formed side by side approximately 4.5 billion years ago, yet recent research published in Nature Astronomy on September 25, 2026, reveals they developed through fundamentally different building processes. Led by researchers at the University of Copenhagen including Professor Anders Johansen and Assistant Professor Haiyang Wang, the study utilized volatile element analysis to uncover distinct formation pathways for the two rocky planets. The authors emphasize that while both planets grew via hybrid accretion involving planetesimals and pebble accretion, the proportions differ drastically. At least 75 percent of Earth's mass originated from young protoplanets that grew through pebble accretion, whereas roughly three-quarters of Mars' mass came from smaller planetesimals. The research methodology combines chemical fingerprints of volatile elements such as sodium, zinc, and potassium with advanced computer models. This approach bypasses ambiguities common in traditional isotope-based methods, offering a more direct window into the primordial conditions of our solar system. These findings carry significant implications for astrobiology and the search for habitable worlds beyond our solar system. Understanding how rocky planets retain volatile substances like water during formation helps scientists predict the habitability of exoplanets in distant star systems.