An international team of scientists has discovered an extreme spike in radiocarbon corresponding to the year 12350 BC during the dusk of the last Ice Age. However, the strength of the event could not be assessed earlier because of the lack of an appropriate model. It has now been identified as the most powerful solar particle storm known to date—a colossal space weather storm that struck Earth 14,300 years ago. This recent finding expands the timeline and intensity of known solar activity and sets a new upper boundary for such solar phenomena.