From: Western University
Posted: Thursday, November 17, 2016
Scientists studying the Chicxulub crater have shown how large asteroid impacts deform rocks in a way that may produce habitats for early life.
Around 65 million years ago a massive asteroid crashed into the Gulf of Mexico causing an impact so huge that the blast and subsequent knock-on effects wiped out around 75 per cent of all life on Earth, including most of the dinosaurs. This is known as the Chicxulub impact.
In April and May 2016, an international team of scientists undertook an offshore expedition and drilled into part of the Chicxulub impact crater. Their mission was to retrieve samples from the rocky inner ridges of the crater – known as the ‘peak ring’ - drilling 506 to 1335 metres below the modern day sea floor to understand more about the ancient cataclysmic event.
Now, the researchers have carried out the first analysis of the core samples. They found that the impact millions of years ago deformed the peak ring rocks in such a way that it made them more porous, and less dense, than any models had previously predicted.
Porous rocks provide niches for simple organisms to take hold, and there would also be nutrients available in the pores, from circulating water that would have been heated inside the Earth’s crust. Early Earth was constantly bombarded by asteroids, and the team have inferred that this bombardment must have also created other rocks with similar physical properties. This may partly explain how life took hold on Earth.
The study, which is published today in the journal Science, also confirmed a model for how peak rings were formed in the Chicxulub crater, and how peak rings may be formed in craters on other planetary bodies.
The team’s new work has confirmed that the asteroid, which created the Chicxulub crater, hit the Earth’s surface with such a force that it pushed rocks, which at that time were ten kilometres beneath the surface, farther downwards and then outwards. These rocks then moved inwards again towards the impact zone and then up to the surface, before collapsing downwards and outwards again to form the peak ring. In total they moved an approximate total distance of 30 kilometres in a matter of a few minutes.
Joanna Morgan, lead author of the study and a professor at Imperial College London's Department of Earth Science and Engineering, said: “It is hard to believe that the same forces that destroyed the dinosaurs may have also played a part, much earlier on in Earth’s history, in providing the first refuges for early life on the planet.”
Gordon Osinski, an associate professor in the Departments of Earth Sciences and Physics and Astronomy at Western University, is one of the co-authors on this study.
“These early results are very exciting and add to the evidence that impact craters can provide habitats for life,” said Osinski. “We have just received samples from this core and one of the things we will focus on here at Western is on documenting evidence for hydrothermal activity after the impact event.”
Beyond Osinski, PhD student William Zylberman from Western's Department of Earth Sciences, former Western graduate student Annemarie Pickersgill and former Western Postdoctoral Fellow Ludovic Ferrière are also co-authors on the study. A number of current Western graduate and undergraduate students will be involved in the analysis of these core samples in the coming months.
Ultimately, the team is looking for evidence of modern and ancient life in the peak-ring rocks. They also want to learn more about the first sediments that were deposited on top of the peak ring, which could tell the researchers if they were deposited by a giant tsunami, provide them with insights into how life recovered, and when life actually returned to this sterilised zone after the impact. The hydrothermal habitats that the Western team are investigating will be key to answering these questions.
“The formation of peak rings in large impact craters,” published in the journal Science, can be read here: http://science.sciencemag.org/content/354/6314/836
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ABOUT THE INTERNATIONAL EXPEDITION TO THE CHICXULUB IMPACT CRATER
The expedition was conducted by the European Consortium for Ocean Research Drilling (ECORD) as part of the International Ocean Discovery Program (IODP). The expedition is also supported by the International Continental Scientific Drilling Programme (ICDP). The expedition would not have been possible without the support and assistance of the Yucatán Government, Mexican federal government agencies and scientists from the National Autonomous University of Mexico (UNAM) and the Centro de Investigación Científica de Yucatán (CICY).
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