The largest asteroid impact zone in the world has been discovered in Australia. A pair of markings are each measured to be at least 125 miles in diameter.
Analysis reveals the geological feature was formed by a massive asteroid more than 300 million years in the past, which likely split into two pieces from atmospheric friction before striking the ground.
The impact was responsible for a widespread extinction that vastly altered the biological makeup of the planet. However, no extinction event can be definitively tied to this collision, and there is no distinct geological layer in the strata of the Earth that provides a means of definitively dating the event. When a separate asteroid impact 66 million years ago ended the age of the dinosaurs, the blast sent a layer of iridium around the planet that was easily detected by geologists.
"The two asteroids must each have been over 10 kilometers (about 6 miles) across - it would have been curtains for many life species on the planet at the time. Large impacts like these may have had a far more significant role in the Earth's evolution than previously thought," said Andrew Glikson from the Australian National University's School of Archaeology and Anthropology.
The first of these markings was discovered in 2010, and researchers at the time declared it to be the third-largest meteor basin in the world. It is possible that the impact occurred more than 300 million years ago, researchers theorize. Dating of the basin is uncertain due to the nature of the rocks in the area, which are between 300 and 600 million years old.
A geothermal research project drilled over 1.25 miles under the surface of Warburton Basin in Central Australia, revealing a region where rock melted due to tremendous heat and pressure, forming glass. This material may have been created by a tremendous impact with an asteroid, investigators determined.
The crust of the Earth in this area, also known as the Alice Springs region, is nearly 19 miles thick. Magnetic modeling revealed the presence of two large domes in the crust, consistent with features that would be formed if the upper layer of the planet rebounded following a major impact.
Analysis of this ancient feature could reveal previously unknown information about the history of asteroid impacts as well as their influence on the geological record, including extinctions. Glikson believes events like the one that formed this massive basin may have played an important role in the development of life on Earth.
The Vredefort crater in South Africa is 100 miles across and was formed 2 billion years ago in an impact believed to be the largest energy release ever seen on Earth.
Discovery of the remainder of the ancient impact crater was published in the journal Tectonophysics.