SINE

Here is what your Jet Propulsion Laboratory writes:

Jet Propulsion Laboratory, 3/6/2003

NASA retrieved and edited 11 12 2008

"It is hard to imagine that one of the largest impact craters on Earth, 180-kilometers (112-mile) wide and 900-meters (3,000-feet) deep, could all but disappear from sight, but it did.

"Chicxulub, located on Mexico's Yucatan peninsula, eluded detection for decades because it was hidden (and at the same time preserved) beneath a kilometer of younger rocks and sediments. Most scientists now agree it's the ‘smoking gun’ -- evidence that a huge asteroid or comet indeed crashed into Earth's surface 65 million years ago causing the extinction of more than 70 percent of the living species on the planet, including the dinosaurs. This idea was first proposed by the father and son team of Luis and Walter Alvarez in 1980.

"The view from space lets scientists see some of Chicxulub's surface features that are not nearly so obvious from the ground. Satellite images showing a necklace of sink holes, called cenotes, across the Yucatan's northern tip are what first caught the attention of NASA researchers … in 1990. They were among the first to propose Chicxulub as the impact site linked to the mass extinctions that occurred at the end of the Cretaceous and beginning of the Tertiary geological ages, called the K/T boundary.

‘We were ignorant of the existence of a crater,’ says [NASA researcher Dr. Kevin] Pope, now an independent geologist, ‘We were working on a project on surface water and Mayan archaeology when we saw this perfect semi-circular structure in [satellite] images …. We were fascinated and got the magnetic and gravity data from the area collected earlier by the Mexican petroleum company, who had been looking for oil. Their data showed a large, remarkably circular structure that they had identified as an impact crater.’ Pope and his colleagues reasoned that the cenotes resulted from fractures in the buried crater's rim and that the area within the cenote ring corresponded with the crater's floor.

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