Comet Theory

Comet theory

I believe that a collision with a giant asteroid or comet change the shape of life on Earth forever?
It is widely agreed that such an object -- 10 kilometers across -- struck just off the coast of the Yucatan peninsula 65 million years ago.
According to scientists who maintain that dinosaur extinction came quickly, the impact must have spelled the cataclysmic end.
For months, scientists conclude, dense clouds of dust blocked the sun's rays, darkening and chilling Earth to deadly levels for most plants and, in turn, many animals. Then, when the dust finally settled, greenhouse gases created by the impact caused temperatures to skyrocket above pre-impact levels.
In just a few years, according to this hypothesis, these frigid and sweltering climatic extremes caused the extinction of not just the dinosaurs, but of up to 70 percent of all plants and animals living at the time.
Evidence
Impact Crater
This 150-kilometer-wide crater lies just off the Yucatan peninsula. Scientists calculate that it was blasted into Earth by a 10-kilometer-wide asteroid or comet traveling 30 kilometers per second -- 150 times faster than a jet airliner.
Scientists have concluded that the impact that created this crater occurred 65 million years ago. The date corresponds perfectly to the date of the dinosaur extinction.
Rare Metal
The metal iridium, which is similar to platinum, is very rare on Earth's surface but is more common in asteroids and in molten rock deep within the planet.
Scientists have discovered levels of iridium 30 times greater than average in the Cretaceous/Tertiary (KT) boundary, the layer of sedimentary rock laid down at the time of the dinosaur extinction.
Melted Rock
These pieces of once-molten rock, called impact ejecta, are evidence of an explosion powerful enough to instantly melt bedrock and propel it more than a hundred miles from its origin.
Ranging in size from large chunks to tiny beads, impact ejecta are common at or near the... [continues]

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