A possible impact structure has been discovered in marine sediments off the West African coast. Named Nadir Crater, its structure closely resembles a complex crater and provides an opportunity for planetary researchers to better understand impacts on marine environments. Impact craters in an ocean form very differently than on land because the water absorbs so much of the incoming energy, leaving no permanent record of the event. Understanding how craters form in marine environments is critical because ~70% of Earth’s surface is covered with water, which suggests that impacts into oceans should have been relatively common throughout Earth’s history.

Uisdean Nicholson from Heriot-Watt University in Edinburgh initially discovered this possible impact structure when reviewing seismic data from off the coast of Africa. Nadir Crater is 8 kilometers wide and, based on numerical modeling, was created by an asteroid 400 meters in diameter. Subsequent age dating of microfossils from nearby oil wells indicates that the impact occurred approximately 66 million years ago. This age is close to that of the well-documented Chicxulub impact event, leading researchers to consider whether the two impacts could be related. One possible scenario is that Earth crossed a dense asteroid field, akin to a meteor shower, and was consequently struck by both the Chicxulub and Nadir asteroids in quick succession.

Despite Nadir Crater’s similarity to a traditional complex crater, confirmation of the impact origin would require directly drilling into the Nadir structure to determine the presence of shocked minerals that develop exclusively due to the extreme shock pressures and temperatures of impact events. If Nadir Crater is confirmed as an impact crater, this structure will significantly add to our understanding of the preserved impact record on Earth, how craters develop in a marine environment, and the geologic conditions around the time of the extinction of the dinosaurs. READ MORE