Scientists have uncovered new clues about the giant space rock that slammed into Earth 66 million years ago and triggered one of the biggest extinction events in the planet’s history.
Their new findings suggest that the object was not an ordinary asteroid, but an extremely rare type of meteorite that is seldom found on Earth today.
The study, published in Science Advances, was carried out by researchers from the University of British Columbia (UBC) along with scientists from France, Belgium and Austria.
By studying tiny traces of the impactor preserved in ancient rocks, the team concluded that the object was most likely a rare type of carbon-rich meteorite known as a CO chondrite, or Ornans-type chondrite.
The impact marked the end of the Cretaceous Period and led to the extinction of about 75% of all species on Earth, including all non-avian dinosaurs. While scientists have known for decades that a massive asteroid impact caused the disaster, identifying exactly what kind of space rock struck Earth has remained a major challenge.
To solve the mystery, the researchers used highly sensitive nickel isotope analysis on samples taken from a thin layer of clay that formed around the world after the impact. This clay layer, often called the K–T or K–Pg boundary, contains tiny remnants of the vaporized meteorite.
Dr. Philippe Claeys, a visiting professor at UBC and professor at Vrije Universiteit Brussel, said recovering information about the impactor is extremely difficult because almost the entire meteorite was completely vaporized when it struck Earth. Only minute traces remain preserved in the clay layer.
The new analysis revealed that the impactor closely matched the chemical signature of CO chondrites. These meteorites are considered some of the oldest and least altered materials in the solar system, preserving information from its earliest days.
Unlike many other carbonaceous chondrites, CO chondrites contain relatively low amounts of volatile elements such as carbon, zinc, water and especially sulfur. This finding is important because some scientists had suggested that sulfur carried by the impactor itself may have played a major role in causing the global environmental collapse. The new research instead suggests that the enormous cloud of dust and debris blasted into the atmosphere by the impact was likely the main factor that blocked sunlight, cooled the planet and disrupted ecosystems worldwide.
CO chondrites are exceptionally rare. Carbonaceous chondrites account for only about 5% of meteorites collected on Earth, and CO chondrites represent only a small fraction of that already uncommon group.
The asteroid that struck Earth was estimated to be about 10 to 15 kilometers (6 to 9 miles) wide and crashed into the planet at roughly 64,000 kilometers (40,000 miles) per hour. The impact carved out the enormous Chicxulub crater, now buried beneath Mexico’s Yucatán Peninsula.
Scientists are still trying to determine where this rare object came from.
It may have originated in the distant outer asteroid belt near Jupiter or another debris-rich region of the outer solar system. Whatever its birthplace, researchers say the dinosaurs were extraordinarily unlucky to have crossed paths with such an unusual visitor from space.
