The Great London:
Mexico

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.

Professor Joanna Morgan, lead author of the study from the 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. We are hoping that further analyses of the core samples will provide more insights into how life can exist in these subterranean environments."

The next steps will see the team acquiring a suite of detailed measurements from the recovered core samples to refine their numerical simulations. Ultimately, the team are 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, and provide them with insights into how life recovered, and when life actually returned to this sterilised zone after the impact.

Source: Imperial College London [November 17, 2016]

An 800-year-old Mexican skull decorated with turquoise mosaic, for decades believed to have been a masterpiece of Mixtec indigenous art is a forgery, a Dutch museum and media said Saturday.

>The National Museum of Ethnology in the western university city of Leiden made the shock discovery after an intensive four-year study on the skull, one of only around 20 in existence world-wide.

"Radiometric dating showed the skull and the turquoise are from the correct time period and origin and are authentic," the museum said on its website.

"But alas: further investigation showed a 20th-century glue was used (to mount the mosaic)," the museum said.

The teeth are also false "as it was too well preserved for a skull that lay underground for centuries," Dutch daily Trouw reported.

The museum bought the piece in 1963 for the equivalent of around $20,000 (19,000 euros) and was seen as a striking example of ancient Mesoamerican art.

An investigation into possible skull-duggery was launched after the museum's conservator Martin Berger received a telephone call back in 2010 from a French colleague in Marseille, Trouw said.

The colleague told Berger they received a similar skull from a private collection and that person who donated the art had doubts about its authenticity.

Berger and his colleagues travelled to a Paris-based laboratory where the Dutch-owned skull was analysed and where "we realised that ours was also a bit more 'modern' than we thought".

Berger told the paper he suspected the fake was mounted by a Mexican dentist back in the 1940s or 1950s, when Mexican archeological sites were subjected to large-scale plunder and dealing in artworks like those of the Mixtecs was a lucrative business.

Asked whether he was disappointed by the revelation, Berger told the newspaper: "No. In actual fact it's given us a bizarre story and that's exactly what museums want to do, to tell stories. It remains as one of our masterpieces -- except, we've changed the information on the sign board."

In any case, said Berger, the skull is only a "partial forgery".

"The skull as well as the turquoise are unique archaeological material. Only, the Mixtecs themselves didn't do the glueing," he said.

Similar Central American crystal skulls housed in museums in Paris, London and Washington, D.C. believed to have been pre-Colombian, were revealed to be fake in a scientific study published in 2008.

Source: AFP [November 26, 2016]

An international research team is formalizing plans to drill nearly 5,000 feet below the seabed to take core samples from the crater of the asteroid that wiped out the dinosaurs.

The group met last week in Merida, Mexico, a city within the nearly 125-mile-wide impact site, to explain the research plans and put out a call for scientists to join the expedition planned for spring 2016. The roughly $10 million in funding for the expedition has been approved and scheduled by the European Consortium for Ocean Research Drilling (ECORD) — part of the International Ocean Discovery Program (IODP) — and the International Continental Scientific Drilling Program (ICDP).

Dinosaurs and other reptiles ruled the planet for 135 million years. That all changed 65.5 million years ago when a 9-mile-wide asteroid slammed into the Earth, triggering a series of apocalyptic events that killed most large animals and plants, and wiped out the dinosaurs and large marine reptiles. The event set the stage for mammals — and eventually humans — to take over. Yet, we have few geologic samples of the now buried impact crater.

Sean Gulick, a researcher at The University of Texas at Austin Institute for Geophysics (UTIG), and a team of scientists from the U.K. and Mexico are working to change that. The team is planning to take the first offshore core samples from near the center of the impact crater, which is called Chicxulub after the seaside village on the Yucatán Peninsula near the crater’s center.

The team, led by Gulick and Joanna Morgan of Imperial College London, will be sampling the crater’s “peak ring” — an enigmatic ring of topographically elevated rocks that surrounds the crater’s center, rises above its floor and has been buried during the past 65.5 million years by sediments.

A peak ring is a feature that is present in all craters caused by large impacts on rocky planetoids. By sampling the Chicxulub peak ring and analyzing its key features, researchers hope to uncover the impact details that set in motion one of the planet’s most profound extinctions, while also shedding light on the mechanisms of large impacts on Earth and on other rocky planets.

“What are the peaks made of? And what can they tell us about the fundamental processes of impacts, which is this dominant planetary resurfacing phenomena?” said Gulick, who is also a research associate professor at the UT Jackson School of Geosciences. UTIG is a research unit of the Jackson School.

The researchers are also interested in examining traces of life that may have lived inside the peak ring’s rocks. Density readings of the rocks indicate that they probably are heavily broken and porous — features that may have served as protected microenvironments for exotic life that could have thrived in the hot, chemically enriched environment of the crater site after impact. Additionally, the earliest recovery of marine life should be recorded within the sediments that filled in the crater in the millions of years after the impact.

“The sediments that filled in the [crater] should have the record for organisms living on the sea floor and in the water that were there for the first recovery after the mass extinction event,” Gulick said. “The hope is we can watch life come back.”

The expedition will last for two months and involve penetrating nearly 5,000 feet beneath the seabed from an offshore platform. The core will be the first complete sample of the rock layers from near the crater’s center.

Once extracted, the core will be shipped to Germany and split in two. Half will be immediately analyzed by an international team of scientists from the U.S., U.K., Mexico and other nations, and half will be saved at a core repository at Texas A&M University for future research needs by the international community.

The team also includes researchers from the National Autonomous University of Mexico (UNAM) and Centro de Investigación Científica de Yucatán (CICY). Scientists interested in joining the mission must apply by May 8, 2015. For more information on the mission and the application process, see the European Consortium for Ocean Research Drilling’s call for applications.

Source: University of Texas at Austin [April 06, 2015]