Australia: the world's largest crater could be found in New South Wales

Southern New South Wales in Australia may be home to the world's largest asteroid impact structure, scientists say, but it is yet to be excavated. 

The current largest asteroid crater is the Vredefort impact structure in South Africa which measures nearly 300km wide. However, the new, yet to be confirmed, crater is suspected to be around 520km in diameter, according to a recent study published in the journal Tectonophysics. The crater is suspected based on magnetic patterns, as scientists suspect there could be a massive, buried impact structure beneath the Murray Basin in New South Wales.

Dubbed the Deniliquin structure, it is estimated to be around three times larger than the one behind the extinction of dinosaurs and lies beneath millions of years of sediments. 

The Chicxulub crater in the Yucatan peninsula in Mexico, which is thought to be created by the asteroid that wiped out the dinosaurs is around 150km wide, said researchers from the University of New South Wales in Australia. The researchers think that the Deniliquin crater may have been caused by an asteroid impact on Earth about 420 million years ago, and if true, will be the largest known asteroid impact structure on Earth.

Asteroid craters are difficult to spot as they may be buried beneath sediments over millions of years or concealed by several factors like erosion. But new discoveries can unearth signatures of impact structures, such as “ejecta” mater. 

Asteroid impacts also coincide with mass extinction events on Earth, like the one that wiped out non-avian dinosaurs about 66 million years ago. But new research suggests the Earth and other planets in the solar system may have been subject to more impacts until around 3.2 billion years ago.

Researchers say there are at least 38 confirmed and 43 potential impact structures on Earth, ranging from small craters to large, buried structures, and the underlying Earth's crust may respond with an elastic rebound and the dome structure, which may erode, could be all that's left from the original structure. The Deniliquin impact's evidence is based on geophysical data from the surface, the timing also coincides with the Late Ordovician mass extinction event.