Nothing rubs them out
Why Is the Moon Covered in Holes?
Earth is hit just as often. The difference is that Earth does not keep the marks.
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Step 1 of 5
A crater is a splash, not a dent.
The rock arrives so fast that it does not push a hole so much as blast one. The ground is thrown outward in a ring, which is why craters are round even when the impact came in at an angle.
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Step 2 of 5
Earth is hit just as often.
The Moon is not a special target. It sits right beside us and takes a similar share of impacts. The difference is entirely in what happens afterwards.
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Step 3 of 5
On Earth, three things rub the marks out.
Wind and rain wear craters down, plants and sediment fill them in, and the surface itself slowly recycles as continents move and volcanoes resurface the ground.
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Step 4 of 5
The Moon has none of them.
No air, so no wind and no rain. No water. No plate movement worth the name. A footprint left there in 1969 is still crisp, and so is a crater from four billion years ago.
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Step 5 of 5
So the Moon is a record of what Earth went through.
The pockmarked face is a diary of the early solar system, when there was far more loose rock flying about. Earth lived through the same bombardment and quietly erased the evidence.
The dark patches are enormous old craters that flooded with lava and set smooth.
The short version
The Moon keeps every impact scar because it has no air, water or moving crust to erase them — Earth is hit as often but does not keep the marks.
Try it yourself
Drop a marble into a tray of flour with cocoa dusted on top. You get a bowl, a raised rim and pale rays thrown outward, just like a real crater.