August 29, 2010

Second Meteorite Impact Helped Wipe Out Dinosaurs

A new study theorizes that the dinosaurs were wiped out 65 million years ago by at least two meteorite strikes rather than one.

Scientists previously thought that a huge meteorite impact occurred in the Gulf of Mexico, wiping out the dinosaurs in one fell swoop.

New evidence, however, suggests that a second impact occurred in the Ukraine, according to a BBC News report on Friday.

The study findings were published in the journal Geology by a team lead by Professor David Jolley of Aberdeen University.

The idea that a meteorite impact killed the dinosaurs was first proposed in 1980.  The discovery of the Chicxulub Crater in the Gulf of Mexico helped to confirm the theory.

The discovery of a second impact crater suggests the dinosaurs were wiped out by a "double whammy" meteorite strike.

The Boltysh Crater in the Ukraine was first reported in 2002.  However, it was uncertain exactly how the timing of the event related to the Chicxulub impact, until now.

Scientists examined the "pollen and spores" of fossil plants in the layers of mud that filled the crater.  They discovered that after the impact, ferns quickly colonized the devastated landscape.

Ferns have an amazing ability to bounce back after a catastrophe.  Layers full of fern spores are considered to be a good indicator of past impact events.  These are known as "fern spikes."

However, the scientists stumbled on an unexpected discovery.

They found a second "fern spike" in a layer three feet above the first, suggesting that there was another meteorite impact.

Professor Simon Kelley of the Open University told BBC News, "We interpret this second layer as the aftermath of the Chicxulub impact."

This proves that the Boltysh and Chicxulub impacts did not occur at the same time.  They struck several thousand years apart, which is the length of time between the two "fern spikes."

Kelley also told BBC: "It is quite possible that in the future we will find evidence for more impact events".

The researchers believe that dinosaurs may have fallen victim to a meteorite shower raining down over thousands of years, rather than being wiped out by a single impact.

Professor Monica Grady, a meteorite expert at the Open University who was not involved in the study, told BBC "One possibility might be the collision of Near Earth Objects".

NASA recently launched a program known as "Spaceguard."  It will monitor these types of Near Earth Objects to help provide an early warning system of possible future collisions.


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