Which asteroid killed dinosaurs

The enduring puzzle has always been where the asteroid or comet originated, and how it came to strike the Earth. And now a pair of Harvard researchers believe they have the answer. Baird Jr. That finding falls in line with research from other astronomers. The pair claim that their new rate of impact is consistent with the age of Chicxulub, providing a satisfactory explanation for its origin and other impactors like it. This is important because a popular theory on the origin of Chicxulub claims the impactor is a fragment of a much larger asteroid that came from the main belt, which is an asteroid population between the orbit of Jupiter and Mars.

Evidence found at the Chicxulub crater and other similar craters that suggests they had carbonaceous chondrite. The new study seals the deal, researchers said, by finding asteroid dust with a matching chemical fingerprint within that crater at the precise geological location that marks the time of the extinction. The study is the latest to come from a International Ocean Discovery Program mission co-led by The University of Texas at Austin that collected nearly 3, feet of rock core from the crater buried under the seafloor.

Research from this mission has helped fill in gaps about the impact , the aftermath and the recovery of life. An iridium spike in the geologic layer found all over the world is how the asteroid hypothesis was born.

In the new study, researchers found a similar spike in a section of rock pulled from the crater. In the crater, the sediment layer deposited in the days to years after the strike is so thick that scientists were able to precisely date the dust to a mere two decades after impact.

Researchers estimate that the dust kicked up by the impact circulated in the atmosphere for no more than a couple of decades — which, Gulick points out, helps time how long extinction took. In addition to iridium, the crater section showed elevated levels of other elements associated with asteroid material. This angle was particularly destructive because it allowed the asteroid's impact to eject a large amount of dust and aerosols into the atmosphere.

Gulick pointed to his colleague's evidence in the region to support the simulations for the angled hit, including the asymmetrical structure of the crater, the position of upwarped bent upward mantle rocks, the unique sediment sequences in cores gathered from the region and, in particular, the absence of a distinct type of rock, called evaporites, in the cores, like halite and gypsum.

Gulick's team estimated that the impact would have vaporized the evaporite rocks, sending gigatons of sulfur in the form of sulfur aerosols, as well as gigatons of carbon dioxide, into the atmosphere. The material thrown into the atmosphere consisted largely of pulverized rock and droplets of sulfuric acid, which came from sulfate-rich marine rocks, known as anhydrite, that vaporized during the asteroid strike, according to a study published in the journal Nature Geoscience.

This cloud of microscopic material created a shroud around the planet, reducing incoming solar heat and light. The resulting long-term cooling drastically altered the planet's climate. A study in the journal Geophysical Research Letters found that the average temperature in the tropics plummeted from 81 degrees Fahrenheit 27 degrees Celsius to 41 F 5 C.

As incoming sunlight dimmed, photosynthesis waned and the base of the food chain on land and in the ocean collapsed, bringing down the dinosaurs and many other animals. Meanwhile, the airborne sulfuric acid led to lethal acid rain that rained for days following the impact, killing countless marine animals living in the upper parts of oceans, as well as in lakes and rivers, the study found.