comets!

  Crashing Comets, Dead Dinosaurs, and You
What would happen if a comet dinged our planet? It's an ugly picture. Just ask the dinosaurs. They apparently had a bad hair eon when a Manhattan-sized comet or asteroid whonked into Earth 65 million years ago.

dino image The question of why dinosaurs suddenly became extinct at the end of the Cretaceous Period (defined) bedeviled paleontologists for decades. One idea was that a large comet or asteroid smashed into our planet
  and triggered a chain of events -- from earthquakes and tidal waves to radical shifts in climate (think of a prehistoric nuclear winter -- that spelled dino-doom).

That idea received a big boost in 1991 when scientists discovered the Chicxulub impact crater, a huge buried crater near Mexico's Yucatan Peninsula. That discovery, many scientists concluded, was the "smoking gun" that ended the argument over the reason for the dino-demise. But other evidence added considerable weight to the idea that the dinosaurs died suddenly and didn't just gradually fade from the landscape.

Paleontologist Peter Sheehan and a team from the Milwaukee Public Museum conducted a painstaking, three-year study of dinosaur fossil remains in the Hell Creek Formation of Montana and North Dakota. By thoroughly searching the layers of sedimentary rock that give us our record of the late Cretaceous, they saw that the dinosaurs and their ecosystem were doing just fine until some kind of abrupt extinction event -- such as a crashing comet -- ended the reign of the Dinosauria.

The chance that the Earth will be blasted by a comet or asteroid in our lifetime is small, but some people have tried to calculate it. Here's another take on the danger of a recent cometary impact.

Is Earth nothing but a cosmic punching bag?



The Why Files
back story map More!

nothingThere are 1 2 3 4 5 6 7 8 9 10 11 12 13 documents.
Glossary | Bibliography | Credits | Search