One fell swoop

Despite the conspiracy theories that claim the killing was down to a network of terror, the latest undercover investigations, just made public, reveal that the dinosaurs and the vast majority of animal life on Earth died in a mass extinction about 65 million years ago because of a single hit.

The likely assassin was an enormous body – the Chicxulub meteorite – that smashed into what we now refer to as the Yucatan Peninsula in Mexico. The new research provides compelling evidence that one and only one impact caused the mass extinction, says its lead author Ken MacLeod, associate professor of geological sciences at Missouri University Columbia.

Ken MacLeod

The samples we found strongly support the single impact hypothesis, he explains, they come from very complete, expanded sections without deposits related to large, direct effects of the impact – for example, landslides – that can shuffle the record, so we can resolve the sequence of events well.

MacLeod adds that, What we see is a unique layer composed of impact-related material precisely at the level of the disappearance of many species of marine plankton that were contemporaries of the youngest dinosaurs. We do not find any sedimentological or geochemical evidence for additional impacts above or below this level, as proposed in multiple impact scenarios.

The Chicxulub crater (Credit: NASA)

The Chicxulub impact probably caused massive earthquakes and tsunami, while dust from the impact would have filled the atmosphere, blocking out sunlight, and leading to the death of plants. Temperatures likely also cooled significantly around the globe. MacLeod and many other scientists believe that these effects led to the relatively rapid extinction of most species on the planet.

Nooooooooooooo! (Credit: LBL)

However, not everyone is convinced of the one-hit wonder theory. Princeton University paleontologist Gerta Keller and her collaborators Thierry Adatte from the University of Neuchatel, Switzerland, and Zsolt Berner and Doris Stueben from Karlsruhe University in Germany suggest there is growing evidence that the dinosaurs and their contemporaries were not wiped out by the Chicxulub meteor impact alone.

They say that it was multiple meteor impacts, massive volcanism in India, and climate change culminated in the end of the Cretaceous Period. Keller and her colleagues reason that Chicxulub may have been the lesser and earlier of a series of meteors and volcanic eruptions that pounded life on Earth for more than 500,000 years.

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