One year after the largest geomagnetic storm in two decades, NASA and scientists around the world are still uncovering the Gannon storm’s scientific goldmine. Striking Earth last May, this G5-level storm didn’t cause catastrophic damage, but it packed enough power to disturb everything from satellites in orbit to farmers' GPS-guided tractors on the ground. It was sparked by a massive solar eruption from an active region 17 times the size of Earth, unleashing a series of coronal mass ejections (CMEs) that merged into a superstorm. 

The result? The thermosphere heated to over 2,100°F, transatlantic flights were rerouted, satellites lost altitude, and the ionosphere twisted into unfamiliar shapes.

NASA missions observed never-before-seen particle belts forming between Earth’s Van Allen radiation belts, and huge magnetic waves rippling through the magnetosphere. Even Mars wasn’t spared—NASA’s MAVEN saw auroras sweep across the Red Planet, and Curiosity’s radiation sensors logged the highest surge since it landed. 

Meanwhile, unusual magenta auroras danced above Japan, reaching up to 600 miles high, thanks to rare atmospheric chemistry triggered by the storm’s intensity.

The Gannon storm is now considered the most well-documented geomagnetic storm in history. Its effects continue to rewrite what we know about space weather—and they’re helping scientists better protect astronauts, spacecraft, and critical tech on Earth.