Before Earth became a blue planet teeming with life, it was a barren, rocky world, dry as dust and chemically incomplete.
A new study from the Institute of Geological Sciences at the University of Bern has now traced the planet’s early chemical evolution with unprecedented precision, revealing that the proto-Earth’s composition was finalized within just three million years of the Solar System’s birth.
However, here’s the twist: early Earth lacked the very ingredients necessary for life. Water, carbon compounds, and other volatile elements were missing from the mix. According to the researchers, a cosmic collision, likely with a planet named Theia, delivered the missing pieces and transformed Earth into the life-friendly haven we know today.
The study, published in Science Advances, was led by Dr. Pascal Kruttasch, who is now a Postdoctoral Mobility Fellow at Imperial College London. It was part of his doctoral work at the University of Bern, supported by the Swiss National Science Foundation. Kruttasch and his team used a molecular timepiece, a radioactive isotope called manganese-53, to date the formation of Earth’s chemical signature.
“A high-precision time measurement system based on the radioactive decay of manganese-53 was used to determine the precise age,” Kruttasch explains. “This isotope was present in the early Solar System and decayed to chromium-53 with a half-life of around 3.8 million years.”
With this method, the team could pinpoint the age of materials billions of years old with less than a million years of uncertainty.
Their findings paint a picture of a young Earth formed in the inner Solar System, a region too hot for volatile elements to condense. The gas-dust cloud from which the planets emerged was rich in life-essential elements, such as hydrogen, carbon, and sulfur.
But near the Sun, these elements remained in the gas phase and weren’t incorporated into the rocky materials that built Earth.
“Thanks to our results, we know that the proto-Earth was initially a dry rocky planet,” says Kruttasch. “It can therefore be assumed that it was only the collision with Theia that brought volatile elements to Earth and ultimately made life possible there.”
Theia, a hypothesized planetary body, likely formed farther from the Sun, in cooler regions where water and other volatiles could accumulate. Its impact with Earth, already suspected to have created the Moon, may have also delivered the chemical ingredients for life.
“Our Solar System formed around 4,568 million years ago. Considering that it only took up to 3 million years to determine the chemical properties of the Earth, this is surprisingly fast,” Kruttasch notes.
The study provides empirical data on the timing of Earth’s chemical formation, strengthening the theory that life’s emergence was not a gradual inevitability, but a cosmic accident.
Professor Klaus Mezger, co-author and Professor Emeritus of Geochemistry at the University of Bern, emphasizes the broader implications: “The Earth does not owe its current life-friendliness to a continuous development, but probably to a chance event, the late impact of a foreign, water-rich body.
This makes it clear that life-friendliness in the universe is anything but a matter of course.” The team’s work not only deepens our understanding of Earth’s origins but also reframes the search for life elsewhere. If Earth’s habitability hinged on a lucky planetary collision, then life-friendly worlds may be far rarer than we imagine.
The next frontier, according to Kruttasch, is to unravel the details of the Theia impact. “So far, this collision event is insufficiently understood. Models are needed that can fully explain not only the physical properties of the Earth and Moon, but also their chemical composition and isotope signatures,” he concludes.
As scientists continue to decode the ancient history written in rocks and isotopes, one thing becomes clear: Earth’s story is not just one of formation, but of transformation, shaped by fire, chance, and a cosmic handshake that may have made life possible.
Journal Reference:
- Pascal M. Kruttasch, Klaus Mezger. Time of proto-Earth reservoir formation and volatile element depletion from 53 Mn- 53 Cr chronometry. Science Advances, 2025; 11 (31) DOI: 10.1126/sciadv.adw1280