Scientists at NASA and the University of Kansas say that a mass extinction on Earth hundreds of millions of years ago could have been trrigered by a stear explosion called a gumma-ray burst.
The scientists do not have direct evidence that such a burst activated the ancient extinction.
The strength of their work is their atmospheric modeling - essentially a“what if”scenario.
The scientists calculated that gamma-ray radiation from a relatively nearby star explosion.
hitting the Earth for only ten seconds, could deplete up to half of the atmosphere's protective ozone layer.
Recavery could take at least five years.
With the ozone layer damaged,ultraviolet radiation from the-Sun could kill much of the life on land and near the surface of oceans and lakes,and disrupt the food chain.