2500 years ago, the earth was clobbered by a massive solar storm.
Traces of radioactive particles have been discovered under the Greenland Ice Sheet.
source: Ian Sample, The Guardian
Scientists studying ice nearly half a kilometre beneath the surface found a band of radioactive elements unleashed by a storm that struck the planet in 660BC.
It was at least 10 times more powerful than any recorded by instruments set up to detect such events in the past 70 years, and as strong as the most intense known solar storm, which hit Earth in AD775.
“What our research shows is that the observational record over the past 70 years does not give us a complete picture of what the sun can do.”
Lund University, Sweden