Buried beneath a half mile of snow and ice in Greenland, scientists have uncovered an impact crater large enough to swallow the District of Columbia.

The finding suggests that a giant iron asteroid smashed into what is today a glacier during the last ice age, an era known as the Pleistocene Epoch that started 2.6 million years ago. When it ended only 11,700 years ago, mega-fauna like saber-toothed cats had died out while humanity had inherited the Earth.

The discovery could lead to insights into the ice age climate, and the effects on it from the eruption of debris that would have resulted from such a cataclysmic collision.

“This is the first impact crater found beneath one of our planet’s ice sheets,” said Kurt Kjær, a geologist at the Center for GeoGenetics at the Natural History Museum of Denmark and lead author of the study, published Wednesday in the journal Science Advances.