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A new theory explaining the formation of the residue left by the asteroid, which may have wiped out the dinosaurs, has been proposed by American scientists. The residue contains sand-sized droplets, called spherules. The new theory suggests the asteroid impact, 65 million years ago, produced a vapour cloud that encircled the whole world. The cloud then condensed and droplets of hot liquid rained down.
�This giant impact not only crushes the rock and melts the rock, but a lot of the rock vaporizes,� said Lawrence Grossman, one of the scientists who performed the analysis. �That vapour is very hot and expands outward from the point of impact, cooling and expanding as it goes. As it cools the vapour condenses as little droplets and rains out over the whole Earth.�
There are two other theories that could explain how the droplets formed. The fist proposes that friction between the asteroid and atmosphere melted the surface of the space rock, and small droplets fell as it approached the Earth. The second suggests the droplets splashed out of the Chicxulub impact crater, following the collision.
The new theory is based on the study of spinel � a mineral rich in magnesium, iron and nickel, contained within the droplets.
�Their paper is an important advance in understanding how these impact spherules form,� said Frank Kyte, associate professor of geochemistry at the University of California, USA. �It shows that the spinels can form within the impact plume, which some researchers argued was not possible.�
Sedimentary, or layered rock is formed when small bits of eroded earth settle and are compressed by further layers settling on top. One such layer is of particular interest because it has been found in rocks all around the world, and contains unusual materials. The layer was formed 65 million years ago, around the time the dinosaurs and many other creatures died out. The layer contains iridium � a material common in asteroids, but very rare on Earth. It is the presence of this iridium layer that led scientists to believe a giant space impact caused the dinosaurs� demise.
More info: American Museum of Natural History
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