The research, led by Curtin University in partnership with the Queensland University of Technology (QUT), challenges long-held assumptions about the Hadean Eon more than 4 billion years ago, suggesting repeated asteroid bombardment was a major driver of Earth’s evolution rather than simply leaving temporary scars on its surface.
Published in the journal Science, the study argued that the immense energy released by frequent impacts penetrated deep into the planet’s interior, heating the mantle and preventing the early crust from stabilising.
Lead author Professor Tim Johnson, from Curtin’s Frontier Institute for Geoscience Solutions, said the findings paint a picture of an Earth that was far more dynamic and volatile than previously believed.
“Large asteroid impacts are often thought of as isolated events that briefly reshape a planet’s surface before geological processes take over,” Johnson said.
“Our research shows they had far more profound and long-lasting consequences. The early solar system was an incredibly violent environment, with collisions occurring far more frequently than they do today.
“The enormous energy released by these impacts had to be absorbed somewhere, and much of it was transferred into Earth’s interior, keeping the crust hot, weak and partially molten for extended periods.
“While those conditions made it difficult for early rocks to survive, they also promoted the formation of silica-rich crust that ultimately became the foundation of the continents we see today.”
Co-lead author Professor Craig O’Neill from QUT said advanced modelling demonstrated that the effects of major impacts persisted long after the initial collisions.
“Rather than being confined to the impact site, much of the energy was transferred into Earth’s mantle, generating heat that caused mantle material to rise, melt and produce enormous volumes of magma,” O’Neill said.
“Our results suggest the Hadean Earth did not possess stable tectonic plates resembling those operating today. Instead, the crust remained thin, mobile and continuously recycled as repeated impacts drove widespread melting over tens to hundreds of millions of years.”
The researchers said the findings also help explain one of geology’s enduring mysteries: why virtually no rocks survived from Earth’s first 500 million years and why stable continental crust only began to emerge after asteroid impacts became less frequent.
Johnson said the timing of this transition closely aligns with evidence preserved on the moon.
“The lunar record shows that by around 3.9 billion years ago, the global effects of impact heating had declined significantly,” he said.
“That’s also when Earth begins preserving continental crust in the geological record, making it unlikely that the two events are simply coincidental.”
Researchers from Macquarie University also contributed to the study, titled Impact heating and the hidden Hadean, which provides fresh insight into how the violent conditions of the early solar system shaped the planet that would eventually become home to life.
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