A team of Australian researchers has found new evidence that suggests the world's largest known asteroid impact structure is buried deep in southeast Australia. The structure, known as the Deniliquin structure, is thought to be about 1,000 kilometers in diameter and was created by an asteroid impact that occurred about 445 million years ago.
The researchers used a technique called gravity gradiometry to map the structure of the Earth's crust beneath Deniliquin. Gravity gradiometry measures the difference in gravity between two points, which can be used to map the density of the underlying rocks.
The researchers found that the Deniliquin structure is associated with a large anomaly in the Earth's gravity field. This anomaly is thought to be caused by a large mass of dense rock, which is consistent with the presence of an impact structure.
The researchers also found that the Deniliquin structure is surrounded by a ring of hills. These hills are thought to have been formed by the impact, as the ground rebounded after the asteroid hit.
The discovery of the Deniliquin structure is significant for several reasons. First, it is the largest known asteroid impact structure on Earth. Second, it is the first impact structure to be found in southeast Australia. Third, the impact that created the Deniliquin structure is thought to have been a major event in Earth's history. It is possible that the impact contributed to the Late Ordovician mass extinction event, which occurred about 445 million years ago. This event wiped out about 85% of marine species and 60% of all land vertebrates.
The discovery of the Deniliquin structure is a reminder that Earth is constantly bombarded by asteroids and comets. While most of these objects pose no threat to life on Earth, a large impact could have devastating consequences. The researchers are continuing to study the Deniliquin structure to learn more about its size, age, and impact on Earth's history. They hope that this research will help us to better understand the risks posed by asteroid impacts and to develop strategies for mitigating these risks.
The following are additional details about the Deniliquin structure:
- It is thought to be about 10 times larger than the Chicxulub impact structure, which is the crater that caused the dinosaur extinction event 66 million years ago.
- The impact that created the Deniliquin structure is thought to have released the equivalent of 100 billion megatons of TNT. This is about 100 million times more powerful than the largest nuclear bomb ever detonated.
- The impact that created the Deniliquin structure would have caused a global tsunami, wildfires, and a dust cloud that would have blocked out the sun for months or even years. This would have caused a mass extinction event, similar to the Late Ordovician mass extinction event.
The discovery of the Deniliquin structure is a sobering reminder of the dangers posed by asteroid impacts. It is important to continue to study these objects and to develop strategies for mitigating the risks they pose to life on Earth.
The research is published in the journal Nature Communications.