The Asteroid that killed Dinosaurs
We share an adoption of an article titled ‘Dino-killing asteroid came from beyond Jupiter’ by Adam Mann published in science.org.
Researchers have recently made a groundbreaking discovery about the most infamous space rock in history: the Chicxulub impactor. This asteroid, which struck Earth 66 million years ago and led to the extinction of the dinosaurs, has now been traced back to its cosmic birthplace. The evidence points to it being a carbonaceous chondrite, a rare type of meteorite that originated far beyond the orbit of Jupiter.
The Chicxulub impactor’s identification as a carbonaceous chondrite adds a significant piece to the puzzle of its catastrophic impact. Previous research had suggested this possibility, including the discovery of a small carbonaceous chondrite fragment during a 2016 drilling project into the crater’s remains. This crater, buried beneath the seabed near Mexico’s Yucatan Peninsula village of Chicxulub, had long been associated with the extinction event.
In the latest edition of Science, researchers report a pivotal finding: trace amounts of ruthenium metal in geological layers worldwide that date back to the impact event. These samples exhibit the same isotopic composition as those found in carbonaceous chondrite meteorites. This discovery reinforces earlier findings and provides a stronger basis for the impactor’s classification.
Meenakshi Wadhwa, a planetary scientist from Arizona State University, praised the new results, stating, “It really bolsters the work that’s been done previously. I feel much more confident that what we’re seeing is a carbonaceous chondrite.” The significance of this finding lies in the rarity of carbonaceous chondrites among current impactors. Their classification helps explain the unique and destructive nature of the Chicxulub event.
The hypothesis that a massive asteroid caused the extinction event was first proposed by father-son scientists Luis and Walter Alvarez. Their groundbreaking theory, developed in the 1980s, suggested that an asteroid larger than Mount Everest struck Earth, sending a cloud of ash and dust into the atmosphere and triggering a global winter. This theory gained support when the Alvarezes discovered elevated levels of iridium—a metal common in space rocks but rare on Earth—in a clay layer marking the boundary between the Cretaceous and Paleogene eras.
Further support came in 1998 with evidence of chromium elevations in the K-Pg boundary layer, consistent with carbonaceous meteorites. However, because chromium can be present in terrestrial rocks and may have leached into the layer, its significance was debated. Ruthenium, which is approximately 100 times more abundant in extraterrestrial rocks, proved to be a more reliable diagnostic element.
Cosmochemist Mario Fischer-Gödde and his team at the University of Cologne analyzed the seven stable isotopes of ruthenium in five K-Pg boundary samples. They found uniform proportions across all samples, matching those found in known carbonaceous meteorites. This consistency indicates a shared origin and strengthens the case for the Chicxulub impactor’s carbonaceous chondrite identity.
Carbonaceous chondrites, remnants from the early Solar System, are rich in water, carbon, and volatile molecules. They formed far from the Sun, where such compounds are preserved. These meteorites contributed to Earth’s early development, including the delivery of water and organic molecules essential for life. Today, carbonaceous chondrites constitute less than 5% of meteorites falling to Earth, making the Chicxulub event even more unusual.
The apparent rarity of carbonaceous chondrites in recent history poses an intriguing question: why did such a meteorite strike Earth so recently? Simulations by Simone Marchi and his team at the Southwest Research Institute suggest an answer. Their research indicates that gravitational interactions with the giant planets could occasionally dislodge carbonaceous asteroids from their distant orbits, sending them into the inner Solar System. Such events might occur every few hundred million years, potentially explaining the Chicxulub impactor’s relatively recent arrival.
Understanding the nature of the Chicxulub impactor not only provides insights into its catastrophic impact but also helps planetary scientists trace the movement of space rocks throughout the Solar System’s history. The carbon-rich nature of the impactor likely contributed to the dark, sooty plume that intensified the extinction event by blocking sunlight.
Future research may further classify the Chicxulub impactor within the subtypes of carbonaceous chondrites, potentially linking it to specific regions of the outer Solar System. While current evidence rules out the comet hypothesis—comets, though similar to carbonaceous chondrites, contain additional water ice—a definitive resolution may require a dedicated space mission to collect samples from a comet.
As we unravel the mysteries of the Chicxulub impactor, we gain a deeper understanding of the cosmic forces that shaped Earth’s history and contributed to one of the most dramatic extinction events in our planet’s past.