Billion-year-old impact in Scotland sparks questions about life on land

Embargoed until 00.01GMT 29^th April 2025 

New research from the University of St Andrews has revealed that a meteorite which struck northwestern Scotland occurred about 200 million years later than previously thought, in a discovery that not only rewrites this part of Scotland’s geological history but alters our understanding of the conditions during the evolution of non-marine life on Earth.

Previously believed to have occurred 1.2 billion years ago, the impact created the Stac Fada Member, a layer of rock that holds vital clues to Earth’s ancient past, including how meteorite strikes may have influenced the planet’s environment and life.

Researchers used tiny zircon crystals as geological ‘time capsules’ to date the impact to 990 million years ago.

In a paper published today in Geology, researchers show that the impact event occurred at a similar time to the emergence of some of the earliest known freshwater eukaryotes - the ancient ancestors of plants, animals and fungi. The revised dating suggests these life forms in Scotland were living at a similar time to a meteorite impact.

This raises questions about impacts and how they may have influenced environmental conditions in ways that affected early ecosystems.

Co Author Professor Tony Prave from the School of Earth and Environmental Sciences at the University of St Andrews said “The Stac Fada impact occurred on a landscape sculpted by rivers, lakes and estuaries containing thriving microbial ecosystems. Impacts typically blow away the land surface and create deep craters. What makes Stac Fada unique is that it preserves not only the record of the impact event but also of the actual land surface across which those ancient ecosystems existed prior to the impact and, importantly, how they recovered from such a natural disaster.”

The research was in collaboration between the University of St Andrews, Curtin University in Western Australia, NASA Johnson Space Centre and the University of Portsmouth

Dr Chris Kirkland from the Frontier Institute for Geoscience Solutions Curtin University said “These microscopic crystals recorded the exact moment of impact, with some even transforming into an incredibly rare mineral called reidite, which only forms under extreme pressures. This provided undeniable proof that a meteorite strike caused the Stac Fada deposit…confirming the impact at 990 million years ago.”

Dr Kirkland added “While the impact crater itself has yet to be found, this study has collected further clues that could finally reveal its location. Understanding when meteorite impacts occurred helps us explore their potential influence on Earth’s environment and the expansion of life beyond the oceans.”