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The Question

(Submitted April 28, 2010)

Is it possible that Earth may have encountered GRB radiation in the distant past? If so, would there be any remnant (geological evidence, chemical evidence) to know?

The Answer

Thanks for your question. This is a good question, and it certainly is possible that a nearby GRB beamed in the direction of the Earth has happened since life arose here.

It has been suggested that the Ordovician-Silurian extinction event about 440 million years ago could have been caused by a GRB. There is no evidence falsifying this hypothesis, but there is no evidence establishing it either..
http://en.wikipedia.org/wiki/Ordovician-Silurian_extinction_event

It may be possible to detect historical GRB exposure from rocks on the moon, but it's much harder on the Earth due to tectonic activity and so forth.

We hope that helps.

-Kevin and Hans,
for "Ask an Astrophysicist"

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