A recent study led by scientists from the University of Cologne has provided insights into the origins of the asteroid that caused the extinction of the dinosaurs about 66 million years ago. The research, published in the journal Science, reveals that this catastrophic asteroid likely originated from a region of space beyond Jupiter, in the outer solar system. This discovery sheds new light on the events that led to one of Earth’s most significant extinction events, which saw the disappearance of approximately 70 percent of all species, including the dinosaurs.

The asteroid impact is believed to have occurred near what is now the Chicxulub crater on the Yucatán Peninsula in Mexico. This impact is widely accepted as the primary cause of the mass extinction event that marked the end of the Cretaceous period and the beginning of the Paleogene period. The asteroid, estimated to have been at least 10 kilometers in diameter, struck Earth with such force that it vaporized not only itself but also large quantities of Earth’s crust. The resulting explosion sent fine particles of dust into the stratosphere, effectively blocking sunlight and disrupting the planet’s climate for years. This “nuclear winter” scenario halted photosynthesis and led to a dramatic decline in global temperatures, which ultimately caused the extinction of many species.

The key to understanding the asteroid’s origins lies in the analysis of a specific layer of sediment that was deposited globally following the impact. This sediment layer, which marks the boundary between the Cretaceous and Paleogene periods, contains unusually high concentrations of platinum-group metals, such as iridium and ruthenium. These metals are rare in Earth’s crust but are more common in extraterrestrial objects like asteroids. By analyzing the isotopic composition of ruthenium in this sediment, the researchers were able to trace the asteroid’s origins back to the outer solar system, beyond Jupiter.

Artistic recreation of the impact of a meteorite
Artistic recreation of the impact of a meteorite. Credit: YAYImages / depositphotos.com

Dr. Mario Fischer-Gödde, the lead author of the study, explained that the isotopic composition of the ruthenium found in the sediment matches that of carbonaceous chondrites—asteroids that are believed to have formed in the outer regions of the solar system during its early development. This finding contrasts with other asteroid impacts on Earth, which are predominantly caused by S-type asteroids that originate from the inner solar system, closer to Mars and the asteroid belt.

The research team also compared the ruthenium isotopic compositions from the Chicxulub impact site with those from other impact craters on Earth. They found that over the past 500 million years, nearly all asteroid impacts on Earth have been caused by S-type asteroids from the inner solar system. The Chicxulub event, however, stands out as a rare exception, involving an asteroid from the outer solar system. This makes the Chicxulub impact a unique event in Earth’s geological history.

Professor Dr. Carsten Münker, a co-author of the study, emphasized the rarity of such an impact, stating that the asteroid that caused the extinction of the dinosaurs was a “once-in-a-billion-year” event. The fact that this asteroid came from the outer solar system, a region where such objects are relatively rare, underscores the extraordinary nature of the event that sealed the fate of the dinosaurs and many other species on Earth.

SOURCES

University of Cologne

Mario Fischer-Gödde et al., Ruthenium isotopes show the Chicxulub impactor was a carbonaceous-type asteroid. Science 385, 752-756(2024). DOI:10.1126/science.adk4868

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