(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?
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..
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"