Throughout Earth’s history, our planet has experienced numerous instances of asteroids colliding with it, either making impact on the surface or exploding in the atmosphere. These asteroid strikes, much like volcanoes, are natural processes that have played a role in shaping the Earth’s surface. While most of these asteroid impacts involved small objects, there are some that are terrifyingly big. One such big asteroid crate was the Chicxulub asteroid crater, which is estimated to be 180 km in diameter. This asteroid strike killed off all the dinosaurs. Shockingly, a new study has found an even bigger asteroid strike crater.
A small asteroid had impacted Earth in recent years too. An example is the one in 2013 when a space rock approximately 20 meters in diameter entered Earth’s atmosphere above Chelyabinsk, Russia. It detonated in mid-air, releasing energy equivalent to 500 kilotons of TNT, it injured nearly a thousand people.
However, certain major impacts are associated with mass extinction events. The Alvarez hypothesis, named after scientists Luis and Walter Alvarez, attributes the extinction of non-avian dinosaurs to a massive asteroid strike about 66 million years ago – that left behind the Chicxulub crater.
Largest Known asteroid impact found!
Now, the largest known asteroid impact structure, as per Space.com, has been found beneath the Earth’s surface in southern New South Wales, Australia. The Deniliquin structure spans up to 520 kilometers in diameter, surpassing the previously considered largest Vredefort impact structure in South Africa, which is around 300 kilometers wide.
The Australian continent, including its ancestral Gondwana, has experienced numerous asteroid impacts resulting in various impact structures—ranging from small craters to large, buried formations. When a substantial asteroid collides with Earth, the underlying crust responds with a temporary elastic rebound, forming a central dome. Such domes can erode or become buried over time, preserving the deep-seated “root zone” of the impact structure. Prominent examples include the Vredefort impact structure and the Chicxulub crater in Mexico, associated with the dinosaur extinction.
The Deniliquin structure exhibits characteristics expected of a large-scale impact. Current evidence primarily relies on surface geophysical data. Proof requires physical evidence of shock, which can be confirmed by deep drilling.
The Deniliquin impact likely occurred on Gondwana’s eastern part before its fragmentation into continents, possibly during the Late Ordovician mass extinction event. This event, known as the Hirnantian glaciation stage, led to an 85% species reduction, surpassing the Chicxulub asteroid strike impact. Alternatively, the Deniliquin structure might predate this event, possibly originating in the early Cambrian (around 514 million years ago).