A Hidden Record of a Giant Impact
Scientists from Curtin University have joined researchers from Aix-Marseille University to reveal a giant asteroid strike in Australia 11 million years ago. The evidence does not come from a crater but from a field of tektites, natural glass formed when an asteroid melts rocks at the surface and hurls fragments across large distances. The newly identified tektite field lies mostly within South Australia, offering a fresh window into Earths impact history.
What tektites tell us about the past
Tektites act as tiny time capsules that preserve chemical fingerprints and isotopic clues from Earths ancient shocks. The tektites in this study are distinctive in chemistry and age, setting them apart from the better known Australasian tektite field that formed about 780,000 years ago.
Unusual chemistry and a new age
Lead author Anna Musolino explains that the tektites are unlike any previously seen. They date to roughly 11 million years ago, indicating a completely separate impact event and a second tektite field within Australia. Their chemistry hints at rocks melted from a different arc than the Australasian field.
The search for a crater that no longer exists
Even as the tektites record a cataclysmic event, the corresponding crater remains undiscovered. The absence of a visible crater challenges researchers to combine tektite evidence with geological maps, remote sensing data, and crater models. Understanding when and how often such large impacts occurred is essential for assessing long-term asteroid risk.
Implications for planetary defense
Dating and locating a deep-time impact helps calibrate models of how frequently life-changing collisions occur and informs planetary defense planning. The study demonstrates how tektite fields and glass fragments can complement crater-based methods and broaden our view of Earths vulnerability to cosmic hazards.
The study
The work is led by Emeritus Professor Pierre Rochette with contributions from Anna Musolino, Fred Jourdan, and others. The paper, titled A new tektite strewn field in Australia ejected from a volcanic arc impact crater 11 Myr ago, appears in Earth and Planetary Science Letters, 2025. This discovery shows how glassy remnants can rewrite chapters of Earths history.
How the tektite field was found and what it means
Researchers used field surveys and geochemical analyses to identify a cluster of tektites and distinguish them from other natural glasses. The field seems to reflect ejection from a volcanic arc impact crater, a scenario that highlights the diverse environments in which large asteroid impacts can leave lasting marks on the landscape. The South Australia region proves to be a prime locale for uncovering such hidden chapters of planetary history.
Geological context and long-term significance
The Miocene epoch, about 11 million years ago, was marked by tectonic and climatic activity. The discovery of a giant asteroid impact from this era adds a new dimension to the Australasia tektite complex and suggests there may be other undiscovered tektite fields waiting in different regions. Collectively, these glass fragments help scientists refine estimates of how often large impacts occur and how they shape Earths history.
