In a new research, scientists have determined that after a giant asteroid slammed into Earth some 65 million years ago, the dinosaurs choked on ozone and were eventually killed off.

Ozone (O3) is a gas that is just three little oxygen atoms bounds together, which doesn't make it a candidate for a potent mass murderer.

That's also because the ozone layer is high in the stratosphere. In fact, its ultraviolet-shielding effect makes it very helpful for life.

But, the problems start when you bring ozone down near the surface.

Mix together a soup of hydrocarbons, nitrogen oxides, and sunlight, and we can find ourselves swimming in the stuff, especially in urban areas.

No one knows what safe levels are, but medical studies suggest that lung tissue gets inflamed and damaged quickly at or around 100 parts per billion of O3.

Now, according to a report in Discovery News, a new study puts forth the idea that the Chicxulub impact, long blamed for the extinction of the dinosaurs at the end of the Cretaceous era 65 million years ago, could have done them in by flinging huge amounts of ozone precursor chemicals - nitrogen oxides, methane, and other hydrocarbons - into the air.

According to the researchers' simulation, the impact could have produced enough ozone to raise concentrations in the atmosphere to over 1,000 parts per billion (or 1 part per million), about 10 times the dangerous level for people.

These high O3 levels were probably enough to cause the dinosaurs to keel over in a fit of wheezing and respiratory distress.

The researchers suggest it may explain why the extinction was selective - it killed off 50 percent of all land animals, but spared large crocodiles, frogs, and mammals. (ANI)