Asteroid dust found in impact craters killed dinosaurs

Sixty-six million years ago, a catastrophic mass extinction occurred that completely changed life on our planet. Dinosaurs disappeared from the surface of the earth, along with many other species and families, including ammonites and mosasaurs. The first evidence for a better understanding of this sudden global extinction of life was found in sedimentary strata near Gubbio in Italy and Caravaca in Spain, where a very thin layer of clay forms the boundary between the Cretaceous and Paleogene periods.

In the early 1980s, scientists found in this clay layer remarkably high concentrations of iridium, a rare mineral found in high concentrations in meteorites but very low concentrations in the Earth’s crust. This clay layer is said to have formed from the dust that was created after an asteroid 12 kilometers in diameter collided and evaporated. This discovery was later confirmed by the discovery of the Chicxulub collision crater 180 to 200 kilometers long buried under the surface of the Yucatan Peninsula in Mexico.

Now, more than 40 years later, scientists have discovered the latest evidence linking a global mass extinction to an asteroid impact. An international team of researchers led by scientists from the Vrije Universiteit Brussel tracked the global asteroid dust layer inside the Chicxulub collision crater in Mexico. “The circuit is now finally complete,” says Stephen Goodyres, a lecturer in geochemistry at the Vrije Universiteit Brussel and lead author of the study.

In May 2016, a ring of hills surrounding Chicxulub Crater in Mexico, called the Peak Ring, was tapped by a scientific team from the International Ocean Exploration Program (IODP) and the International Continental Scientific Drilling Program (ICDP) Expedition 364. About 835 meters of rock were brought in To the surface, providing a tremendous amount of new information about the processes that occurred in the crater region during and shortly after the asteroid collision.

The core also recorded in great detail the time interval during which the crater moved from a dynamic environment as ocean water and tsunamis returned to calmer conditions. Based on an extensive geochemical analysis of this portion of the core, the highest concentrations of iridium in a clay-rich period were found in sediments covering the crater circle, beneath limestone from the earliest antiquity.

Iridium is a difficult element to measure in this context due to its low concentrations. That’s why we combined the results of four independent laboratories around the world to make sure we got that right, ”explains Stephen Gooderis. The measured iridium concentrations in the core of the pits correspond to those previously measured at locations around the Gulf of Mexico. Remarkably, we found such concentrations. High in the impact crater itself.During the first hours to months after the collision, the crater was a highly turbulent environment affected by tsunamis, oscillating waves and earthquakes.In addition, hydrothermal fluids coming to the surface from the depth of the crater had also passed through the iridium layer, but they It did not change it significantly. Fortunately, the iridium layer was preserved, thanks in part to the unique location of the core of the pits in low on the soaring peak ring.After orbiting the Earth in the atmosphere for several years, the deposition of this rich dust could have continued With iridium for a few decades after collision, Juderis sums up.

Consequently, the precipitation of this asteroid in the atmosphere places important time limits on the deposition of crater rock just below the iridium layer. This part of the crater returned to a relatively low-energy environment in a much shorter time than previously expected. Besides other time indicators, such as microfossils and helium-3 concentrations, the iridium layer represents the timing of life restoration over the years to thousands of years after impact, indicating a very complex biological response to the rapidly changing environment at zero point. Gulick, a research professor at the University of Texas at Austin and co-chief scientist on the Excavation Expedition. Thus, the drill core for IODP-ICDP Expedition 364 contains an exceptional detailed account of the processes associated with Chicxulub Crater formation and life restoration.

The discovery of a well-defined iridium anomaly in the Chicxulub crater would also reinvigorate the research into the Cretaceous and Paleogene mass extinctions. “With this discovery, we are more able than ever to set precise time limits for the products that were formed as a result of an asteroid collision. Inside the crater, we see a pile of molten, crushed, and fine-grained rocks 130 meters thick that may have been deposited in less than twenty years. With most of it being deposited even on the first day, which is amazingly fast.In many different places around the world, this 20-year period of time is represented by a much thinner bedrock, made up of impacted, molten, and dense material that was thrown from the crater by comparing these sites. Different, we will better understand the exact mechanisms related to the Chicxulub effect that led to the global mass extinction, explains Pim Kaskes, FWO doctoral student at Vrije Universiteit Brussel who works at the core of the drilling. This field is for 30 years of Cretaceous Paleogene research.

The study was published in Science advances.