Moon Sheds Light on Earth’s Impact History

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.


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