Study supports theory of extraterrestrial impact

Researchers have conclusively identified a family of nanodiamonds, including the impact form of nanodiamonds called lonsdaleite, which is unique to cosmic impact.

By University of California, Santa Barbara — Published: March 6, 2012

Images of single and twinned nanodiamonds show the atomic lattice framework of the nanodiamonds. Each dot represents a single atom. Credit: University of California, Santa Barbara

A 16-member international team of researchers that includes James Kennett from the University of California, Santa Barbara, has identified a nearly 13,000-year-old layer of thin, dark sediment buried in the floor of Lake Cuitzeo in central Mexico. The sediment layer contains an exotic assemblage of materials, including nanodiamonds, impact spherules, and more, which, according to the researchers, are the result of a cosmic body impacting Earth.

These new data are the latest to strongly support a controversial hypothesis proposing that a major cosmic impact with Earth occurred 12,900 years ago at the onset of an unusual cold climatic period called the Younger Dryas.

Conducting a wide range of exhaustive tests, the researchers conclusively identified a family of nanodiamonds, including the impact form of nanodiamonds called lonsdaleite, which is unique to cosmic impact. The researchers also found spherules that had collided at high velocities with other spherules during the chaos of impact. Such features, Kennett noted, could not have formed through anthropogenic, volcanic, or other natural terrestrial processes. “These materials form only through cosmic impact,” he said.

The data suggest that a comet or asteroid — likely a large, previously fragmented body greater than several hundred meters in diameter — entered the atmosphere at a relatively shallow angle. The heat at impact burned biomass, melted surface rocks, and caused major environmental disruption. “These results are consistent with earlier reported discoveries throughout North America of abrupt ecosystem change, megafaunal extinction, and human cultural change and population reduction,” Kennett said.

The sediment layer identified by the researchers is of the same age as that previously reported at numerous locations throughout North America, Greenland, and Western Europe. The current discovery extends the known range of the nanodiamond-rich layer into Mexico and the tropics. In addition, it is the first reported for true lake deposits.

In the entire geologic record, there are only two known continent-wide layers with abundance peaks in nanodiamonds, impact spherules, and aciniform soot. These are in the 65-million-year-old Cretaceous-Paleogene boundary layer that coincided with major extinctions, including the dinosaurs and ammonites; and the Younger Dryas boundary event at 12,900 years ago, closely associated with the extinctions of many large North American animals, including mammoths, mastodons, saber-tooth cats, and dire wolves.

“The timing of the impact event coincided with the most extraordinary biotic and environmental changes over Mexico and Central America during the last approximately 20,000 years, as recorded by others in several regional lake deposits,” said Kennett. “These changes were large, abrupt, and unprecedented, and had been recorded and identified by earlier investigators as a ‘time of crisis.’”

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MRS KAREN VERMILYA from MICHIGAN said:

Is the process that creates nanodiamonds similar to that which fuses sand into glass from a lightning strike?

Submitted: 3/10/2012 7:25:21 AM (CST)

BILL SIMPSON from LOUISIANA said:

@ Major Casals
Probably not. Humans don't evolve in that short a period of time. When this thing hit, if you could go back in a time machine and trim a whole lot of hair off the humans you find, and dress them in the clothing of today and bring them back, they could walk down any street tomorrow, unnoticed. And they would be just as smart as we are. (I'm not sure if the Neanderthals had gone extinct 13,000 years ago, or not. They looked different and probably weren't as smart as us.) The modern homo sapiens you would meet would be virtually identical to you. We haven't changed at all in about the last 50,000 years, and not too much in the last 200,000 years. Technological development has made the big difference in the way we live, not intelligence, or human evolution. Our very rapid recent progress is based on the development of mathematics and science which enabled the use of concentrated sources of energy like coal, oil, gas, and uranium to greatly amplify the amount of work we can accomplish. Without them, we go back to the year 1,500 tomorrow.
It doesn't take a VERY big asteroid or comet (comets are the most dangerous ones, because they can come out of nowhere and surprise you before you have a chance to do anything about it, if they are on the wrong course) to do awesome damage. Go on Purdue's 'IMPACT EARTH!' website, and you can send one into Earth. The most surprising thing to me is the damage done by the heat radiation, before the blast has a chance to level everything. The heat is why, when you see pictures of the H-bomb test out in the Pacific, everyone needed to be over 20 miles away. 30 with the giant multi-megaton blasts. That is why you see so many clouds between the photo plane and the giant 5 mile wide fireball. Get within 12 miles and the pilot wouldn't come back. And radiant heat travels at the speed of light. The energy carried by an asteroid or comet more than a quarter mile across would dwarf that produced by all the H-bombs ever tested. Luckily, Earth is a tiny moving target, not easily randomly hit in the emptiness of space. Those bombs are a FAR greater threat. They have the potential to bring our evolution to an abrupt halt.

Submitted: 3/7/2012 10:57:18 PM (CST)