Buried deep in Greenland’s ice sheet lies a puzzling chemical signature that has sparked intense scientific debate. A sharp spike in platinum concentrations, discovered in an ice core (a cylinder of ice drilled out of ice sheets and glaciers) and dated to around 12,800 years ago, has provided support for a hypothesis that Earth was struck by an exotic meteorite or comet at that time.

Our new research published in PLOS One offers a much more mundane explanation: this mystery platinum signature may have originated from a volcanic fissure eruption in Iceland, not space.

The timing matters. The platinum spike occurs near the beginning of our planet’s last great cold period, the Younger Dryas Event. This lasted from about 12,870 to 11,700 years ago and saw temperatures plummet across the northern hemisphere.