New research led by Curtin University and QUT (Queensland University of Technology) has found that repeated asteroid impacts may have been the dominant force shaping the early Earth, delivering large amounts of heat into the planet’s interior and delaying the formation of stable continents.
The study, published in Science, suggests that during the Hadean period – more than four billion years ago – Earth was struck far more frequently than it is today, with each impact injecting energy deep into the planet.
Rather than a relatively stable early planet, the findings point to a much hotter, weaker and more unstable Earth, closer to the extreme conditions long proposed by scientists.
Challenging assumptions about impacts
Professor Tim Johnson doing fieldwork.
The research challenges the idea that large asteroid impacts were simply brief surface events with limited long-term consequences.
Professor Tim Johnson, Lead Author on the study from the Curtin Frontier Institute for Geoscience Solutions within the School of Earth and Planetary Sciences, explained the significance of the findings.
“There is a temptation to think of large impacts as short-lived events that scar a planet’s surface and then pass,” Professor Johnson commented.
“But the early Solar System was full of collisions, and the Moon preserves that history in plain sight. Those impacts carried enormous amounts of energy, and that energy had to go somewhere.”
Professor Johnson noted that the extra heat from impacts would have kept much of the early crust weak and partially molten, making it difficult for rocks to survive. At the same time, those conditions would have helped produce more silica-rich crust, which later became the foundation of the continents.
Energy transferred deep into Earth’s mantle
AI simulation of a massive impact shows the mantle contains both basalt-rich (purple) and basalt-poor (green) regions.
Co-Lead Author Professor Craig O’Neill, from QUT, described how the team’s modelling showed the effects of impacts extended far beyond the moment of collision.
“On the early Earth, much of that energy would have been transferred into Earth’s mantle, the thick layer immediately beneath the crust, as heat,” Professor O’Neill explained.
“That would have caused mantle beneath and around the impact site to rise and melt, producing large volumes of magma.”
The modelling suggests the early crust was thin and unstable for much of the Hadean, rather than a world with strong plates behaving in a familiar modern way.
“Impacts would have helped keep the crust hot, weak and mobile, while driving melting and recycling on a planetary scale for tens to hundreds of millions of years after the initial collision,” Professor O’Neill added.
Explaining the missing rock record
The findings also help explain why almost no rocks survive from the first 500 million years of Earth’s history and why long-lived continents appear to have formed only after the intensity of impacts declined.
Professor Johnson pointed to the timing of this transition as noteworthy.
“It is apparent from the Moon that, by around 3.9 billion years ago, the global effect of impact heating becomes much less important, which is also around the time Earth begins to preserve continental crust. That seems unlikely to be a coincidence,” Professor Johnson observed.
The lunar surface preserves a record of the bombardment history that Earth also experienced but has since erased through geological processes such as plate tectonics, erosion and volcanic activity. By using the Moon as a reference point, the researchers were able to model how the frequency and scale of impacts would have affected conditions on early Earth.
Research collaboration
Macquarie University also contributed to the study, titled Impact heating and the hidden Hadean, which is available online.
Last Updated on June 27, 2026 by Nick Ross