Officially Confirmed. Yarrabubba crater is the world’s oldest recognized impact site.
An impact event or an asteroid strike is a severe and violent geological event caused by the collision of astronomical objects like meteorites, asteroids, comets, with the Earth, and may lead to catastrophic consequences. Impact events have played a significant role in the evolution of the Solar system. Moreover, asteroid bombardment flux is speculated to have had major consequences for the development of the Earth’s surface environment.
The oldest meteorite site.
For many years Vredefort crater has been the oldest and the largest impact structure in the world until now. The impact occurred in South Africa, and it is estimated that when the collapse ceased, the size of the crater was between 180 and 300 km wide. Vredefort crater is estimated to be 2.023 bn years (give or take 4 million years).
However, there is another impact site that is older than Vredefort crater; it is located in Western Australia at the place called Yarrabubba. The size of the structure is 70 km wide.
Yarrabubba was already known to scientists, but its age hadn’t yet been determined.
According to the study published on 21 Jan 2020, shock-recrystallized monazite yields a precise impact age of 2.229 bn years (give or take 5 million years), coeval with shock-reset zircon. This results in the conclusion, that Yarrabubba is the oldest meteorite impact structure on Earth.
Scientists stated that the age constraints establish Yarrabubba as the first meteorite impact to have occurred during the Rhyacian period, which is a second geologic period in the Paleoproterozoic Era, and time in the evolution of the Earth following the transition from the Archaean to the Proterozoic eon.
“Because their crystal structure can incorporate uranium — but not lead — when they crystallize, and uranium will decay to lead at a known rate, we can use the ratios of the uranium and lead isotopes to determine their age”, explained T.M. Erickson. That’s how his team discovered the age of the crater.
The youngest Paleoproterozoic glacial deposit, the Rietfontein diamictite within the Transvaal basin of South Africa, has an age of 2 225 bn years (give or take 3 million years). However, after this period, there are no records of glacial deposits appearance for 400 million years, and scientists are still debating about the causes of this absence.
It is assumed that the Yarrabubba impact could have triggered a climate change by releasing big amounts of CO2 and other greenhouse gases, including water vapor into the Paleoproterozoic atmosphere. Although the Earth’s atmosphere at the time of impact contained only a fraction of the current level of oxygen, scientists think that the climatic forcing effects of water vapor released into the atmosphere through the Yarrabubba impact may have been globally significant. They also have come to the conclusion that its coincidence with the termination of Paleoproterozoic glacial conditions prompts further consideration of the ability of meteorite impacts to trigger climate change.
