As Earth was thawing out at the end of the last ice age, it was hit by a powerful blast from the Sun. The storm would have triggered spectacular displays of the northern and southern lights. And it left an imprint in tree rings. Using that imprint, scientists have found that the storm was the most powerful yet recorded. And they even have a time for the event: the first quarter of the year 12,350 BC.

Solar storms pelt Earth all the time. Most of the storms are small. But big ones can damage or destroy satellites, zap power systems on the ground, and cause other mischief.

The biggest one ever seen took place in 1859. It knocked out telegraph systems around the world. But scientists have found evidence of even bigger events in the more-distant past.

Some of the events are recorded in tree rings. Charged particles from the storms interact with Earth’s atmosphere to produce a radioactive form of carbon.

Trees take up some of the carbon, which decays to a more stable form at a known rate. So comparing the ratio of carbon isotopes in tree rings can tell us when big storms took place.

Researchers measured the carbon in rings from the end of the ice age. And they developed a new model of chemistry of the atmosphere during such cold periods. Their work showed that Earth was hit by the strongest solar storm yet discovered more than 14,000 years ago.

More about space weather tomorrow.

Script by Damond Benningfield