Answer:
A massive asteroid impact would create long-term changes in the atmosphere and climate of the planet. Upon impact, vaporized dirt and rock would fill the atmosphere, blocking sunlight and creating a state of near-permanent darkness and winter-like conditions. Another dangerous effect of an asteroid strike would be damage to the ozone layer. The energy imparted to the atmosphere by the incoming object would be enough to disrupt the protective layer of ozone high in the stratosphere, drastically increasing the amount of ultraviolet light that made it to the surface. This would increase global cancer rates, affect the growth of plants and animals and possibly lead to genetic mutations over the period of increased exposure. Depending on the size of the asteroid, this could last for as much as two years.
