Why Does the Moon Have More Craters than the Earth?
A long time ago, when the Earth and Moon were very young, many large meteorites crashed into their surfaces, and blasted out huge holes shaped like saucers. These holes are called craters. Three processes help Earth keep its surface crater free. The first is called erosion. Most of the early craters on the Earth have since been eroded by wind and rain, or have been covered over with dirt and rock.
Others lie buried beneath lakes and oceans. The moon has no water or air, so there is no erosion. Everything remains as it was millions of years ago. The chance of a giant meteor crashing into the Earth or moon today is extremely small. The second thing is something called tectonics.
Tectonics are processes that cause our planet’s surface to form new rocks, get rid of old rocks, and shift around over millions of years. Because of tectonics, the surface of Earth is recycled many times throughout its long history. As a result, very few rocks on Earth are as old as the rocks on the Moon. The Moon has not had tectonics for billions of years. That’s a lot more time for craters to form and stay put. The third thing is volcanism.
Volcanic flows can cover up impacts craters. This is a major way impact craters get covered up elsewhere in our solar system, but it is less important than the recycling of crust here on Earth. The Moon once had large volcanic flows way in the past that did cover up many of the bigger earlier impacts, but it has been without volcanism for around three billion years. No wonder there are so many craters on the Moon compared to Earth!