An asteroid or meteor is more likely to hit Earth because Earth is a lot bigger than the Moon, giving a meteoroid more area to hit! But we can see many thousands of craters on the Moon and we only know of about 180 on Earth! Why is that?
Full Answer
Earth probably gets hit more often than the moon, being a larger target, but hides the scars much better and the atmosphere stops many of them from doing visible damage. What you see on the moon is a record of every hit in its life. Not so with the Earth where most craters are rendered invisible in short order.
But we can see many thousands of craters on the Moon and we only know of about 180 on Earth! Why is that? The truth is both the Earth and the Moon have been hit many, many times throughout their long 4.5 billion year history.
Once a crater is made on the moon - it’s there forever - or at least until another asteroid/comet smacks into it and another crater covers it up. Even the tiniest impact onto the Moon makes a crater. Here on Earth craters are eroded and resurfaced by plate tectonics. Volcanic eruptions pour smooth lava over other craters.
Vredefort crater in South Africa is the largest known impact crater on Earth—almost 200 miles across! At over 2 billion years old, it is also one of the oldest. Because of erosion over this long time period, the crater is a bit difficult to see. Credit: NASA.
Why does the Moon have so many craters while Earth has so few? On Earth, impact craters are harder to recognize because of weathering and erosion of its surface. The Moon lacks water, an atmosphere, and tectonic activity, three forces that erode Earth's surface and erase all but the most recent impacts.
The first reason is that Earth's surface is continuously changing because we live on a geologically active planet. Impact craters are relatively shallow, so these “dents” in Earth's rocky crust (the surface bit we can see with our eyes) can be easily buried or wiped out by erosion.
There are so few craters on the Earth because most have been destroyed due to plate tectonics and erosion.
Understanding Earth The first reason is that Earth's surface is continuously changing because we live on a geologically active planet. Impact craters are relatively shallow, so these “dents” in Earth's rocky crust (the surface bit we can see with our eyes) can be easily buried or wiped out by erosion.
But we can see many thousands of craters on the Moon and we only know of about 180 on Earth! Why is that? The truth is both the Earth and the Moon have been hit many, many times throughout their long 4.5 billion year history. This view of the Moon's cratered South Pole was seen by NASA's Clementine spacecraft in 1996.
Credit: NASA/LRO. The Moon has almost no erosion because it has no atmosphere. That means it has no wind, it has no weather, and it certainly has no plants. Almost nothing can remove marks on its surface once they are made.
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.
The main difference between the two is that Earth has processes that can erase almost all evidence of past impacts. The Moon does not. Pretty much any tiny dent made on the Moon’s surface is going to stay there. Three processes help Earth keep its surface crater free. The first is called erosion.
These act together to break apart and wear down the ground. Eventually erosion can break a crater down to virtually nothing. Lake Manicouagan , a ring-shaped lake in Quebec, Canada, is all that remains of a crater from a massive impact over 200 million years ago. Credit: NASA/GSFC/LaRC/JPL/MISR Team.
Once something hits the Moon, that event becomes frozen in time. Earth, on the other hand, simply brushes these impact craters off and moves on with its life. No wonder there are so many craters on the Moon compared to Earth! Credit: NASA/JPL-Caltech. article last updated April 23, 2020.
That’s a lot more time for craters to form and stay put. The third thing is volcanism. Volcanic flows can cover up impact 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.