You've probably heard about the asteroid impact that led to the extinction of the dinosaurs.
But that's by no means the only impact that Earth has experienced.
In fact, scientists have found almost two-hundred impact craters all over the world.
An important question, then, is how often do these impacts occur?
Is the rate steady, or has it changed over time?
If we play back the impacts that have occurred over the last 650 million years, we find that
the impact rate seems to speed up at around 290 million years ago.
But that might only be because older craters are harder to find.
They may have been erased by weathering, vegetation, and geological processes.
To test this, scientists have now looked to our nearest neighbor in space, the Moon.
The Moon and the Earth are close enough that they should share the same impact history,
but the Moon isn't subject to the forces that might erase impact craters on Earth.
Using rock abundance data from the Diviner instrument on Lunar Reconnaissance Orbiter,
scientists were able to catalog and date the large, relatively young lunar craters, the
ones that formed in just the last billion years.
And when they plot those over time, they see the same speed-up at around 290 million years
ago.
The change in the cratering rate isn't just an artifact of the crater record on Earth
- it's real.
The Moon is like a time capsule, preserving the geological history of the Earth-Moon system.
By studying the Moon, we can learn a great deal about the history of our own planet.