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A Solar Storm Rocked the Earth 2,700 Years Ago—and Left Traces in Greenland’s Ice

Radioactive chemicals, preserved for thousands of years, reveal that a powerful solar storm swept over our planet around 660 BCE.

ByKatherine J. WuNOVA NextNOVA Next
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Ejections of particles from the Sun's surface can buffet the Earth. If strong enough, they can take down power grids and compromise communication and navigation operations. Image Credit: solarseven, iStock

Some 2,700 years ago, a massive solar storm bombarded Earth. High-energy particles pinged into the atmosphere, sending a cascade of unstable atoms raining down onto the planet’s surface.

Today, only faint chemical echoes of this ancient collision remain. But according to a study published yesterday in the journal PNAS, scientists have now uncovered these radioactive remnants of the tempest in ice cores from Greenland.

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Though this particular storm, which battered Earth sometime around 660 BCE, is one of many recorded, it’s thought to be at least 10 times more powerful than any detected in the past 70 years—suggesting that we might still have incomplete picture of “what the Sun can do,” study author Raimund Muscheler, a geologist at Lund University in Sweden, told Ian Sample at The Guardian.

Were a similar event to occur today, mild to moderate chaos would likely ensue. Solar storms originate from the surface of the Sun, home to a roiling magnetic field in constant flux. Occasionally, bursts of charged particles like protons are belched into space—and if pitched Earthward, the powerful surge of energetic particles could trigger massive power outages, discombobulate navigation and communication systems, incapacitate commercial aircraft, and even compromise operations aboard the International Space Station. These storms can also temporarily erode the Earth’s ozone layer, allowing more ultraviolet radiation to reach vulnerable lifeforms below, reports George Dvorsky at Gizmodo.

The Earth has recovered from events like this before. But these cataclysmic impacts leave their mark: Each time sun-sourced particles slam into our planet’s atmosphere, they also generate radioactive isotopes of elements like carbon, beryllium, and chlorine, which eventually drift down to the ground, embedding themselves in tree rings and ice cores.

By examining the solar fossil record in two ice cores drilled out of Greenland’s ice sheets, Muscheler and his team were able to uncover such events from before satellite and ground-based technologies started tracking solar storms. Spikes in beryllium and chlorine isotopes indicated that, during the seventh century BCE, the world was rocked by a storm that might be among the strongest ever recorded.

It’s possible that events like these happen as frequently as once a millennium, Dvorsky at Gizmodo reports. Researchers are still a ways away from definitive estimates—but studying these prehistoric storms might be our best bet at forecasting future flare-ups. For now, it seems clear that “these enormous events are a recurring feature of the Sun,” Muscheler told Charles Q. Choi at Live Science. “There might be more that we have not yet discovered.”

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