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Dartmouth Researchers Say a Comet Killed the Dinosaurs

In a geological moment about 66 million years ago, something killed off almost all the dinosaurs and some 70 percent of all other species living on Earth. Only those dinosaurs related to birds appear to have survived. Most scientists agree that the culprit in this extinction was extraterrestrial, and the prevailing opinion has been that the party crasher was an asteroid.
Not so, say two Dartmouth researchers. Professors Jason Moore and Mukul Sharma of the Department of Earth Sciences favour another explanation, asserting that a high-velocity comet led to the demise of the dinosaurs.
 
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Ancient asteroid may have triggered global firestorm on Earth

A new look at conditions after a Manhattan-sized asteroid slammed into a region of Mexico in the dinosaur days indicates the event could have triggered a global firestorm that would have burned every twig, bush and tree on Earth and led to the extinction of 80 percent of all Earth's species, says a new University of Colorado Boulder study.
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Dinosaur extinction: Scientists estimate 'most accurate' date

Scientists believe they have determined the most precise date yet for the extinction of dinosaurs.
Researchers from Glasgow University were part of an international team that has been investigating the demise of the dinosaur.
By using dating techniques on rock and ash samples, they established the creatures died out about 66,038,000 years ago - give or take 11,000 years.
 
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Dinosaur-killing asteroid was a binary asteroid

The infamous space rock that slammed into Earth and helped wipe it clean of large dinosaurs may have been a binary - two asteroids orbiting each other.
The dino-killing asteroid is usually thought of as a single rock with a diameter of 7 to 10 kilometres, but it may really have been two widely separated rocks with that combined diameter.
 
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Fragment of meteorite 'that killed the dinosaurs' found

A Romanian geologist claims to have discovered a fragment of the meteorite that killed off the dinosaurs. Marius Paniti says the segment of rock could have come from the gigantic meteorite that hit the earth wiping out prehistoric life. Paniti from the University of Timisoara claims to have found a huge fragment of what was the biggest meteorite that has ever fallen on Earth in a cave at Cara's Severin County, in south west Romania.
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Title: Modelling the onset of photosynthesis after the Chicxulub asteroid impact
Authors: Noel Perez, Rolando Cardenas, Osmel Martin, Reinaldo Rojas

We do a preliminary modelling of the photosynthetic rates of phytoplankton at the very beginning of the Paleogene, just after the impact of the Chicxulub asteroid, which decisively contributed to the last known mass extinction of the Phanerozoic eon. We assume the worst possible scenario from the photobiological point of view: an already clear atmosphere with no ozone, as the timescale for soot and dust settling (years) is smaller than that of the full ozone regeneration (decades). Even in these conditions we show that most phytoplankton species would have had reasonable potential for photosynthesis in all the three main optical ocean water types. This modelling could help explain why the recovery of phytoplankton was relatively rapid after the huge environmental stress of that asteroid impact. In a more general scope, it also reminds us of the great resilience of the unicellular biosphere against huge environmental perturbations.

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New Suspects in a 65 Million-Year-Old Mystery

Calculations show that the Chicxulub meteorite was certainly big enough to have triggered eruptions at its antipode. But it seems the Deccan Traps probably lay at least 1,000 miles away from Chicxulub's antipode at the time, though it would take just a little error in our assumptions about the speed and direction of Mexico's and India's motion to put India over the antipode.
Another possibility is that Chicxulub was one of a swarm of large meteorites to strike at the same time, all from a fragmented asteroid or comet. There are roughly contemporary craters in the North Sea and Ukraine and a disputed one off the west coast of India. Against this, recent analysis suggests only a single iridium layer, implying a single big impact.

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Impact study: Princeton model shows fallout of a giant meteorite strike

Seeking to better understand the level of death and destruction that would result from a large meteorite striking the Earth, Princeton University researchers have developed a new model that can not only more accurately simulate the seismic fallout of such an impact, but also help reveal new information about the surface and interior of planets based on past collisions.
Princeton researchers created the first model to take into account Earth's elliptical shape, surface features and ocean depths in simulations of how seismic waves generated by a meteorite collision would spread across and within the planet. Current projections rely on models of a featureless spherical world with nothing to disrupt the meteorite's impact, the researchers report in the October issue of Geophysical Journal International.

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Paleontologist Kenneth Lacovara is looking deep in a New Jersey silt mine for the exact moment, 65 million years ago, when all dinosaurs perished.
That secret could be harder to uncover if the fossils here can no longer be unearthed after a housing and retail development is built on this open pit.
Lacovara, an associate professor of biology at Drexel University in Philadelphia, looks at this 40-foot deep hole at the end of a dirt road and sees a line in the sand where the Cretaceous period begins and ends. Below that line are dinosaurs, above it, not a single one.

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Cretaceous–Tertiary extinction event
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La célèbre limite Crétacé-Tertiaire plus ancienne qu'estimée jusqu'à présent

En analysant par la méthode de la cyclostratigraphie des séries sédimentaires marines prélevées dans les océans Indien et Atlantiques lors d'anciennes campagnes océanographiques des programmes internationaux « ODP » et « DSDP », une équipe de chercheurs français et américains a pu démontrer la corrélation des cycles sédimentaires avec les variations des paramètres orbitaux de la Terre et dater la limite Crétacé-Paléogène, soit à 65.59±0.07 Ma, soit à 66±0.07 Ma. Cette deuxième proposition est plus en accord avec les dernières données radiométriques, ce qui recule dans le temps cette limite de 405 000 ans par rapport à ce qui est actuellement admis.
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