Key Takeaways:
- The Yarrabubba site in Western Australia boasts the oldest known impact crater on Earth, dating back over 2.2 billion years, indicating a significant event in our planet’s history.
- Despite the massive scale of the impact, erosion and tectonic activity have obscured the Yarrabubba crater’s physical features over time, leaving behind only subtle geological clues.
- Scientists employed sophisticated dating methods involving the analysis of microscopic minerals to precisely determine the age of the Yarrabubba rocks, setting a new standard for dating ancient geological events.
- The Yarrabubba impact coincided with a pivotal period in Earth’s climate history, potentially contributing to the transition from a global ice age to more familiar environmental conditions through the release of water vapor into the atmosphere.
- Celestial impacts, such as the one at Yarrabubba, have played crucial roles in shaping Earth’s climate and geological development throughout history, highlighting the interconnectedness of celestial events and terrestrial phenomena.
Approximately 70,000 meteorites, which are fragments of space objects that collide with Earth, have been identified by scientists. However, only 190 of these have left discernible impact craters that scientists could recognize.
As per a research article published in the journal Nature Communications, the oldest known impact site is located in Western Australia, roughly 500 miles northeast of Perth. Around 2.2 billion years ago, a colossal meteorite created a crater spanning 43 miles in diameter at this location.
Presently, the site known as Yarrabubba, characterized by a dusty red hue, no longer exhibits a distinct crater due to erosion and the shifting of tectonic plates.
Timmons Erickson, a scientist affiliated with NASA’s Johnson Space Center and the primary author of the study, explained to Business Insider, “There is minimal exposed rock at Yarrabubba, and most of it displays a reddish stain.”
Nevertheless, remnants of the cataclysmic event persist in the form of rocks. A small elevation at the center of the site, named Barlangi Rock, consists entirely of rocks that formed under the intense conditions generated by the meteorite’s impact.
Through the dating of these rocks, Erickson and his colleagues were able to precisely determine the age of the Yarrabubba crater. Their findings indicated that it predates any other known crater on Earth by over 200 million years.
Situated in the remote outback of Western Australia, the Yarrabubba site lies approximately 40 miles from the nearest town, Meekatharra, accessible via a gravel track. In 2014, Erickson journeyed to the site and collected 200 pounds of rocks for analysis.
To ascertain the age of these rocks, Erickson’s team submerged the samples in water at their laboratory and subjected them to 120,000 volts of electrical energy. This process caused the rocks to disintegrate into microscopic grains of zircon and monazite. These minerals retain radioactive elements such as uranium, enabling scientists to determine their age.
Analysis revealed that the rocks from Yarrabubba are 2.229 billion years old, with a margin of error of plus or minus 5 million years.
The next oldest known impact site on Earth is the vast Vredefort Dome in South Africa, dating back 2.02 billion years, followed by Ontario’s Sudbury impact structure, which formed 1.85 billion years ago.
Erickson emphasized that the age of the Yarrabubba crater isn’t the only remarkable aspect of the discovery. The impact also occurred during a pivotal period in Earth’s history, characterized by a transition towards conditions more akin to the present.
According to the study, when the Yarrabubba meteorite collided with Earth, it likely struck a massive ice sheet. This is because 2.2 billion years ago, the planet was emerging from a phase of global glaciation known as a “snowball Earth.”
Through simulations, Erickson’s team demonstrated that such an impact could have released up to 100 billion tons of water vapor into the upper atmosphere. This influx of water vapor may have contributed to an intensification of the greenhouse effect in Earth’s atmosphere, leading to a warming trend that brought about the end of the ice age.
Erickson explained, “Water serves as a highly effective greenhouse gas, surpassing even carbon dioxide.”
The Yarrabubba meteorite represents just one instance of celestial bodies influencing Earth’s climate. For example, the 6-mile-wide asteroid that struck Chicxulub, Mexico, 66 million years ago initiated widespread wildfires, triggered a towering tsunami, and released vast quantities of sulfur into the atmosphere.
The resulting haze blocked sunlight, cooling the planet and ultimately contributing to the extinction of the dinosaurs. Additionally, acid rain and fallout from the impact led to rapid acidification of the oceans, resulting in a mass marine extinction event.
The authors of the study noted that such “extraterrestrial bombardment” likely played a significant role in shaping Earth’s development over time, particularly when impacts occurred in specific regions of the planet.
Erickson remarked, “Frequently, it appears that the impact must occur in a particular location on Earth to have a significant impact on the planet’s climate. For instance, the Chicxulub impact site on the Yucatan peninsula happened to contain substantial salt and gypsum deposits, which released enormous quantities of sulfur into the atmosphere, leading to catastrophic acid rain.”
