The first chapter of Earth’s formation moved quickly. New research shows that our planet locked in its basic chemical makeup within about three million years of the Solar System’s birth.
That type of fast chemical coalescence helped build a world, but there was a catch: those early ingredients didn’t include much of what life needs.
In details shared from a recent study, the picture that emerges is stark.
Early Earth had very few volatile organic compounds (VOCs). The planet was short on water and carbon-bearing compounds, so life didn’t get the jumpstart it needed.
These critical supplies likely arrived later, after the planet’s interior reservoirs had formed.
Scientists at the University of Bern’s Institute of Geological Sciences point to a later event that changed Earth’s chemistry enough to make life possible.
Studying Earth’s early formation
Scientists timed Earth’s early formation using a short-lived radioactive marker – manganese-53, which decays into chromium-53.
“A high-precision time measurement system based on the radioactive decay of manganese-53 was used to determine the precise age,” explained Dr. Pascal Kruttasch, first author of the study.
“This isotope was present in the early Solar System and decayed to chromium-53 with a half-life of around 3.8 million years.”
That half-life is well suited to events in the first few million years, providing a clear “stopwatch” for very old materials.
Using this chronometer, the team reached age estimates with an accuracy better than one million years – razor sharp for the dawn of planet-building.
With those numbers, they conclude that the proto-Earth’s fundamental composition was established no later than three million years after the Solar System formed.
Understanding the timeline
The timing points to a planet that formed quickly but started out dry. By the time Earth’s key reservoirs were in place – the mantle, crustal ingredients, and core – the volatiles were largely missing.
That means life’s essentials had to arrive later, after the early blueprint was already set.
The team compared chromium isotopes in ancient meteorites with those in carefully selected Earth rocks. Meteorites act as time capsules from early planet formation.
Earth rocks, even after long and complex histories, can preserve subtle isotopic fingerprints that record when major reservoirs separated.
Measuring Earth’s formation timeline
Making such fine measurements on materials billions of years old is difficult.
“These measurements were only possible because the University of Bern has internationally recognized expertise and infrastructure for the analysis of extraterrestrial materials and is a leader in the field of isotope geochemistry,” says co-author Klaus Mezger, Professor Emeritus of Geochemistry at the Institute of Geological Sciences at the University of Bern.
That technical capability provides a strong check on the timeline.
The manganese-chromium system is sensitive to the period when the Solar System cooled, solids formed, and planets assembled. With this precision, small shifts in timing appear clearly in the isotopes.
Early Earth formation was dry
Volatile elements are depleted at high temperatures. In the inner Solar System, temperatures were high when the Sun switched on.
Dust and rock could clump and grow, but water and other volatiles struggled to condense and accompany them.
Farther from the Sun, colder conditions allowed ices and gases to persist. The rocky material that built Earth formed in the hot zone, so the planet began with a deficit in water, carbon compounds, and sulfur.
This conclusion is evidence-based. The isotope data fit a scenario in which Earth’s baseline chemistry was set early while volatiles remained scarce nearby.
Slow, local additions of water from the inner region fit the measurements far less well because that region contained little to begin with.
Earth, Theia, and the Moon
If Earth finished its “dry start” early, the water-rich addition needed to come later. One leading candidate is a large collision – an impact by a body that formed farther from the Sun, where volatiles were abundant.
You may have heard of Theia, a Mars-sized object thought to have struck the young Earth and produced the Moon.
If Theia (or a similar body) originated in a colder, volatile-rich region, it could have delivered a crucial payload of water and other ingredients.
That scenario aligns with the data: fast formation followed by a later delivery that changed the planet’s surface environment.
Without that delivery, Earth could have remained a rocky world with little water, even while orbiting within the Sun’s so-called habitable zone.
Implications for life
Location matters, but history matters just as much. Two Earth-sized planets at similar distances from their stars can end up very different if only one receives a late infusion of water.
Timing, source regions, and impact histories determine whether a planet develops oceans and an atmosphere capable of supporting biology.
This reframes how we think about “just right” conditions. Habitability is not guaranteed by orbit alone; it depends on when and how a planet acquires its volatiles, and whether early formation locked in a dry start.
More questions about early Earth formation
Open questions remain about the giant impact. The next step is to investigate the collision event between the proto-Earth and Theia in more detail.
“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,” concludes Kruttasch.
That modeling work will test how a volatile-rich impactor could supply Earth’s water while also explaining the Moon’s makeup and the shared isotope traits seen across both bodies.
With tighter clocks and better simulations, we can keep pressing on a simple, high-stakes question: How did a dry, young Earth become a wet world fit for life?
The full study was published in the journal Science Advances.
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