If you look back far enough into Earth’s hazy, long-forgotten prehistory, things get weird.

Like the battered face of the Moon, our own planet is covered in craters: a scarred legacy of millions of years of brutal, unforgiving asteroid impacts. What’s weird, though, is once you look back about 300 million years, the evidence of this onslaught seems to almost disappear.

For a long time, scientists assumed the comparative rarity of impact craters dating back beyond 300 million years ago on Earth was linked to erosion; environmental processes like weather or tectonic activity had somehow wiped the slate clean, creating what’s known as a ‘preservation bias‘ in the scientific record.

Not so, according to a new study, which suggests an even simpler reason for the invisible asteroids.

It’s not that our terrestrial record of asteroid impacts vanished after the fact. Rather…