by Terrence Aym

Created on: January 24, 2013   Last Updated: January 25, 2013

Life on Earth, while robust, is also fragile. The biosphere can only support higher lifeforms within a very narrow range. Mass extinction events have occurred numerous times in Earth's past and no doubt will happen many more times in the future.

Various cataclysmic events happen that place all or most life at high risk. Among the planet-threatening events that have destroyed much of the life on Earth are: massive super volcanoes erupting, gigatons of methane gas changing the atmosphere and robbing animals of life-giving oxygen, gigantic space rocks—asteroids and comets miles wide—slamming into the planet and plunging the world into darkness…

But perhaps the worst wild card of all are the killer gamma rays that could burn through the protective atmosphere of Earth and scour the surface of the planet destroying virtually all life above ground. Supermassive stars exploding into supernovas or hypernovas can create such a wave of killer radiation that will travel at light speed. If a relatively nearby star goes supernova, the cosmic gamma radiation created could reach the Earth with enough intensity to wipe out the human race.

What are cosmic rays?

Cosmic rays are highly charged particles of matter that cross interstellar space. Most cosmic rays don't radiate outward in a straight direction because they are warped by gravity and magnetic fields when traveling distances measured in light years.

A particular type of cosmic ray, however, known as the gamma ray, is unaffected by fields and can cross huge distances of interstellar space. Its course is not warped because gamma rays have similar properties to light.

Gamma ray bursts are created by titanic events: the collision of black holes, neutron stars or a hypernova. The energy released by such events is known to be the most powerful and dangerously destructive in the universe.

It's believed at least one mass extinction occurring in Earth's distant past was triggered by a bombardment of gamma rays.

While that event was many hundreds of millions of years ago, evidence emerged during 2012 that Earth was hit by a blast of radiation—a blast much weaker than the one thought to have caused a great extinction. This radiation hit Earth during the Middle Ages and its origin puzzled researchers.

New study suggests gamma ray burst

A cosmic explosion created by the massive collision of neutron stars or two black holes sent a shock wave of charged particles racing toward Earth. That's the conclusion of new research

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