New research shows Earth was born dry, lacking water and life-essential chemicals. A later collision with Theia delivered water and volatiles, transforming Earth into a habitable planet capable of supporting life.
New research from the University of Bern reveals that when Earth first formed, it was a dry, inhospitable planet, lacking water and the chemical building blocks needed for life. Scientists now believe that a massive collision with a planetary body called Theia later delivered the essential ingredients that transformed Earth into a habitable world.
The study shows that within just three million years after the Solar System began forming, Earth’s basic chemical composition was already set. However, these early materials contained almost no water or carbon compounds. The inner Solar System, where Earth resides, was too hot for volatile elements to condense and integrate into forming planets, meaning the proto-Earth started out as a barren rock. Only bodies forming farther from the Sun, in cooler regions, could accumulate these life-essential elements.
By analyzing isotopes in meteorites and terrestrial rocks, the researchers reconstructed the timeline of Earth’s early chemistry. Using manganese-53 decay as a precise “clock,” they determined the proto-Earth’s chemical signature formed in less than three million years — a remarkably fast process on a cosmic scale.
The key turning point came when the proto-Earth collided with Theia, a Mars-sized body that likely formed in the colder, outer Solar System. This impact delivered water and volatile compounds to Earth, making it capable of supporting life. Without this chance event, Earth might have remained a lifeless, dry planet.
“This shows that Earth’s habitability was not guaranteed,” explains Dr. Pascal Kruttasch, lead author of the study. “Life-friendly conditions depended on a rare cosmic event, highlighting how delicate the balance is for planets to become suitable for life.”
Published in Science Advances, the study provides new insight into planetary formation and the origins of life on Earth. Future research will focus on understanding the details of the Theia collision, including how it shaped both Earth and the Moon’s chemical and physical characteristics.