Iridium levels of submerged crater support dinosaur extinction theory

A new study has analyzed asteroid dust recently discovered in the Chicxulub asteroid crater. The findings further support the theory that the dramatic impact was the cause of the mass extinction event that wiped out the dinosaurs.

Roughly 66 million years ago, a 7 mile (11 km)-wide asteroid – or perhaps comet fragment – slammed into the Earth’s surface, carving out a massive impact crater. Its remnants can still be observed in the modern-day Yucatan Peninsula in Mexico.

The aftereffects of such a cataclysmic event would have been devastating to life on Earth. Back in the 1980s, scientists discovered asteroid dust – containing elevated levels of the rare element iridium – within the geological layer of the Earth dating back to the time that the dinosaurs went extinct.

This suggested that particles relating to the impact, including vaporized elements of the asteroid itself, spread around the world quickly after the strike. They blocked out the light cast by the Sun and, in the process, triggered a global winter.

However, this geological evidence was not enough to convince the entirety of the scientific community that an asteroid strike was the culprit for the extinction event.

Some believe that the Cretaceous-Paleogene extinction was instead the result of a massive and prolonged series of volcanic eruptions. According to this theory, the fallout from these eruptions inexorably altered our planet’s climate and reshaped the biosphere in a way that proved deadly to 75 percent of life on Earth.

The authors of the new study believe that they have finally "closed the circle" on the mystery, by finding asteroid dust in the Chicxulub impact crater that matches the particles embedded in the 66 million-year old layer discovered in the 80s.

The researchers made their discovery following an analysis of rock core extracted from a region of the 125 mile (201 km)-wide impact site located on the ocean floor. It was found that the core sample, which was dated to just two decades after the asteroid struck, had elevated iridium levels that matched the samples taken from the ancient geological layer.

"We are now at the level of coincidence that geologically doesn’t happen without causation," explains Sean Gulick, a research professor at the University of Texas' Jackson School of Geosciences, and co-author of the new study. "It puts to bed any doubts that the iridium anomaly [in the geologic layer] is related to the Chicxulub crater."

The examination was carried out by four independent laboratories, in order to assure the validity of the findings. It was discovered that the greatest concentrations of iridium were located in a 5-cm (2-in) section of core taken from the uppermost section of the crater’s peak ring.

There were also numerous other elements, both asteroid-based and earthbound, shared between the core samples and measurements taken from the extinction-era geological layer taken from 52 sampling sites.

A paper on the study has been published in the journal Science Advances.

Source: The University of Texas at Austin