Around
450 million years ago, the Earth was devastated by a terrible disaster that
annihilated around 85 per cent of all marine species – at the time, the
predominant form of life on the planet.
Known
as the Late Ordovician Extinction, it was the second most devastating blow to
life on Earth during its history – worse even than the notorious impact-related
event that forced the dinosaurs in the line of extinction 65 million years ago.
Geological evidence points to a sudden plunge in global temperatures, though
the cause remains uncertain. But one possibility is the explosion of a death
star relatively very close to Earth.
Analysis
of the effects of a gamma-ray burst by researchers at the University of Kansas
and the US space agency NASA suggests it would have triggered the destruction
of the Earth’s protective ozone layer, as it allowing intense ultraviolet
radiation from the Sun to reach the surface. This would have wiped out many
life-forms in the upper layers of the oceans – including plankton, a key part of
the marine food chain.
It’s
also possible that the changes in atmospheric chemistry triggered by the blast
may, in turn, have it been triggered global cooling – though whether this would
be enough to account for the Ordovician ice age is unclear.
What
is certain is that the giant stars capable of producing gamma-ray bursts are
spread throughout the cosmos. As such, it is not only life on Earth that’s
threatened by them. According to research by known Professor James Annis of the
Fermi National Accelerator Laboratory, Illinois, gamma-ray bursts may be then
regularly sterilize their host galaxies; if that’s true, our chances of finding
life elsewhere in the very Milky Way would be much reduced.
