MORE THAN 400 MILLION years ago, the Earth was a very different place than it is today. The climate, encouraged by excessive levels of greenhouse gases, was hot enough to ensure no water was locked away at the poles. Sea levels were a hundred metres higher than today and, in their balmy waters, sea life had exploded – dominating life on Earth.
Then this all changed. Inexplicably, the climate cooled, glaciers formed at the poles, sea levels plummeted and more than 85 per cent of the Earth’s species died out. The Late Ordovician mass extinction, as it has come to be known, was one of the most catastrophic extinction events in the planet’s history, but what caused the climate to take such a dramatic U-turn?
One explanation is that the Earth was the unwilling recipient of a massive dose of gamma radiation gifted to us by a distant star, dying a violent death. Gamma ray bursts (GRBs) are the most powerful cosmic explosions we know of. When a massive star explodes in a supernova explosion, sometimes, as if in a fit of raw fury, the star will spew intense beams of deadly gamma radiation into the cosmos.
If the Earth was at the receiving end of such an outburst all those millennia ago, gamma radiation would have smashed into the atmosphere – destroying the protective ozone layer and blanketing the planet in suffocating blanket of smog that blocked sunlight and sent the climate into the tailspin that resulted in the death of more than three-quarters of life on Earth.
Well, get your best apocalypse trousers on, if some scientists are to be believed, the Earth could be on the receiving end of another dose of gamma rays.