An asteroid impact could be mistaken for an attack by a Middle Eastern country and ?could certainly trigger a regional if not global nuclear exchange,? says Brian Marsden, an astronomer at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. This assumes that the country hit by the asteroid has the ability for a nuclear response.

While several countries actively search for asteroids and are aware of the potential dangers, many nations do little research into this threat. Small asteroids that could cause significant localized or even regional damage hit Earth every few centuries, and though none are known to be on a collision course with Earth at the moment, experts say there is always a risk that one could strike without warning.
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One less thing to worry about: astronomers have decided that we are much less likely to get wiped out by a big asteroid than previously thought. The odds are only about 1 in 5,000 that an asteroid big enough to wipe out civilization will hit the Earth in the next 100 years, a team at Princeton University reported, which is far lower than previous estimates of 1 in 1,500.

Research on asteroids that have hit the Earth in the past, like the one that wiped out the dinosaurs 65 million years ago, shows that a collision with a large asteroid at least half a mile in diameter could kill a quarter of the world?s population. The same research has shown that these large asteroids strike the planet regularly, every 100 million years or so.
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More evidence has been found proving that those sweet little birds, hopping and chirping about in your yard, are related to the dinosaurs of the distant past. A 130-million-year-old fossil of a feathered dinosaur has been discovered by farmers in China. It turns out that the impact that wiped out the dinosaurs didn’t kill off all of them-it left a few smaller ones behind that were covered with feathers.

Dr. Mark Norell, of the American Museum of Natural History, said the fossil was about 2 ? feet long, the size of a duck with a long tail. “It shows us that these creatures looked more like weird birds than giant lizards,” he said. Despite being small, this dinosaur is related to the mighty Tyrannosaurus rex.
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Invisible asteroids and other cosmic bodies made of a new form of matter may pose a threat to Earth, according to an Australian physicist.

Robert Foot of the University of Melbourne claims that a meteorite composed of mirror matter, which is an invisible dark matter that is said to make up over 95 percent of the universe, could impact the Earth without leaving behind any fragments.

An asteroid made up of mirror matter may have been responsible for the Tunguska blast, which destroyed acres of Siberian forest in 1908. Scientists have attributed the mysterious destruction to a meteor impact, but no traces of a meteor have ever been found.
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