The earth has a huge scar: in the area of the Mexican peninsula Yucatan, the remains of a crater, which has a diameter of about 190 kilometers. The so-called Chicxulub crater was presumably caused by an asteroid, which had a diameter of 10 to 15 kilometers and raced according to datings about 66 million years ago into the earth. At the same time, most Cretan animals disappeared from the stage of evolutionary history. Therefore, it is believed that the asteroid impact was responsible for the end of this era.
The new evidence of the effect of the Chicxulub impact has been discovered by researchers led by Johan Vellekoop from the University of Utrecht in marine sedimentary rocks in what is now the US state of Texas. They are about 66 million years old and have literally pertinent characteristics: The researchers found in the rock samples unusually high concentrations of the rare element iridium. According to them, they are very likely from deposits that arose during the asteroid impact. In addition, the researchers found layers of shattered mussel shells. It was very likely that they were caused by the huge pressure of the huge waves that raced around the earth after the impact.
At least seven degrees colder
But the researchers went even further into detail with their investigations: they subjected the rock samples to an analysis method that allows conclusions to be drawn about the water temperatures that once existed when they were first formed. Characteristics of embedded remnants of lipids in the rock serve as a source of information. Comparisons of rocks from before and after impact showed that the temperatures had dropped drastically - presumably by at least seven degrees Celsius, the analysis results suggest.
According to the researchers, this result clearly corroborates the shielding of sunlight by particles that had swirled into the earth's atmosphere. Thus, the demise scenario at the end of the Cretaceous now assumes clearer outlines. The global winter certainly had drastic consequences for life on land and in the seas. Less sunlight and cold temperatures were likely to cause biomass production to collapse. The whole splendor of the Cretaceous wildlife was thus doomed. Only a few species could survive and formed the basis of further evolutionary history on our planet. display
Original work of the researchers:
- PNAS, doi: 10.1073 / pnas.1319253111