A recent study has redefined the timeline of a Scottish meteorite impact, pushing its age from 1.2 billion years to around 990 million years. This shift offers fresh insights into a crucial time in Earth’s history when complex life began to emerge beyond the oceans.
The evidence comes from a rugged rock formation in northwest Scotland known as the Stac Fada Member. Within this rock, researchers found tiny crystals that can accurately mark the moment of impact.
This research was led by Chris Kirkland from Curtin University, with contributions from NASA’s Johnson Space Center. Using a mix of fieldwork and laboratory analysis, the team created a precise timeline of the event.
Kirkland noted, “These microscopic crystals recorded the exact moment of impact, some transforming into a rare mineral called reidite.” This physical record helps anchor the timing of the event amidst a landscape where many terrestrial impact craters lack precise ages. A 2022 review highlighted that only 37 out of 188 known craters worldwide were accurately dated.
The study’s findings not only provide a timestamp for this impact but also connect to a period of rapid changes in life on land. The key player in this revelation is zircon, a resilient mineral that can trap uranium atoms during its formation. By measuring the ratios of uranium to lead isotopes in these zircon crystals, scientists can gauge their age. Reidite, which forms under extreme pressure during impacts, provides additional evidence of the event.
Zircon’s ability to withstand heat and erosion is crucial for dating the impact accurately. Researchers examined shocked zircon and its recrystallized areas, isolating the moment of impact to establish a precise date. This new dating places the Stac Fada event in the early Neoproterozoic—a time marked by shifting continents and evolving atmospheres.
Earlier analyses estimated a date of 1.177 billion years based on minerals found in the same unit, but the new findings suggest that older methods might have identified altered minerals, not true impact products. This new date aligns with earlier evidence of complex, single-celled organisms appearing in nearby rocks.
While the crater responsible for the Stac Fada ejecta remains unidentified, the study provides a framework for scientists to refine their searches. Using geophysical surveys and mapping techniques may help narrow down the options.
Understanding the timing of impacts has broader implications. It allows scientists to draw connections between meteorite strikes and biological or environmental shifts on Earth. The patterns emerging from this research could help in understanding how life adapted and thrived following major disturbances, a vital aspect for climate models and the future of planetary habitability.
The study is published in Geology. For more information, you can check out the research here.
