Our planet earth was hit with massive doses of radiation a long time ago. This may have played a part in our species’ evolution.
The effect of some dying stars, as they throw out megatons of debris, could influence life on earth in its millions of years of evolution. Two studies have been published in the journal Nature about these supernovae and their aftereffects on planets such as our earth.
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Although the cosmic rays that reached earth way back then must have had an impact, they were too weak to cause mass extinctions.
Supernovae eruptions cause heavy elements and radioactive isotopes to be scattered in the surrounding space. Iron-60 is one such isotope and it has a half life of 2.6 million years.
What that means is that any relics from this isotope must have vanished by now from the surface of the earth. If there are any remnants of the isotope, they must have come from more recent events in the cosmos.
A team of researchers found traces of this isotope in the sea beds of the Pacific, Atlantic and Indian Oceans. The supernovae were probably 325 light years away from our provenance in the universe.
"We were very surprised that there was debris clearly spread across 1.5 million years," said Dr Wallner, a nuclear physicist in the ANU Research School of Physics and Engineering.
"It suggests there were a series of supernovae, one after another. "It's an interesting coincidence that they correspond with when the Earth cooled and moved from the Pliocene into the Pleistocene period."
It is to be noted down that iron-60 is many times less common on earth than the sort that is usually found and is given the chemical symbol “Fe”. The methods of detecting the iron-60 on earth were very fine tuned and delicate in their nature.
The explosions, trajectories and masses of the supernovae were also calculated from an in-depth study of this isotope. Two events came to light. One took place 1.7 to 3.5 million years ago.
"The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms," said research leader Dr Anton Wallner from The Australian National University (ANU).
The other one occurred 6.5 to 8.7 million years ago. The space debris seemed to have come from one supernova after another in succession.
When the earth evolved from one ancient geological period into another, these explosions took place. Some say that the cosmic rays from the explosions may have boosted the quantity and quality of the clouds covering the earth.
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The influence these distant messengers of physical particles had may have been visible in the life forms on earth. Certain events in the history of our planet may have had a link with the supernovae explosions which took place so many light years away. It is indeed a possibility although not much can be said about it just yet.