Since long before the dawn of science fiction, humans have been absolutely fascinated with (and fearful of) asteroids – those gigantic space rocks capable of Earth-shattering collisions (and notably responsible for the extinction of dinosaurs). Fortunately, there have only been 190 recorded asteroid hits in the entire 4.5 billion year history of our planet – and new evidence suggests that NSW could be home to the biggest one yet.
Recent research published by two Australian scientists in the journal Tectonophysics suggests that the world’s largest known asteroid impact structure is buried deep beneath the surface near Deniliquin in southern NSW. Spanning up to 520 kilometres in diameter, the ‘Deniliquin structure’ far exceeds the size of the almost 300km-wide Vredefort impact structure in South Africa, which previously held the title as the world’s largest.
Based on magnetic patterns beneath the Murray Basin and geophysical data, the scientists estimate the Denliquin structure was created by an asteroid impact cluster that occurred approximately 445 million years old. This is around the time of the Late Ordovician mass extinction, hinting at its potential involvement in the catastrophic event that wiped out about 85 per cent of Earth’s marine species and 60 per cent of land vertebrates.
The Deniliquin structure has all the hallmarks we’d expect from a mass impact structure, including a seismically defined dome at its centre, a symmetrical rippling pattern in the crust around the structure’s core, and a 30km-deep deformation above a seismically defined mantle dome. This evidence is a strong start, but the scientists will need to drill deep into the structure and collect physical proof to back up their current findings. You can read the full research paper here.