Why Does the Moon Have So Many Craters?

The Moon’s surface is covered with thousands of craters. Most were created when asteroids, meteoroids, and comets struck the lunar surface over billions of years.

But impacts alone do not explain why the craters are still so easy to see. The main reason is that the Moon has very little atmosphere, no rain or flowing water, and far less geological activity to erase its old surface.

Why Does the Moon Have So Many Craters?

The Moon has been exposed to impacts throughout its history. Objects traveling through the Solar System have repeatedly struck its surface, creating craters ranging from tiny pits to enormous impact basins.

Earth has also experienced countless impacts. The difference is that many of Earth’s old craters have been eroded, buried, altered, or destroyed. On the Moon, much of the evidence remains visible.

Frequent impacts + slow surface change = a heavily cratered Moon.

How Do Craters Form on the Moon?

A crater forms when a meteoroid, asteroid, or comet strikes the Moon at high speed. The collision releases enormous energy, excavating material from the surface and leaving a depression.

Material thrown out during the impact, called ejecta, can spread around the crater and form a layer on the surrounding surface.

Impacts Happen at Very High Speeds

Space rocks do not simply fall onto the Moon. They can hit its surface at several kilometers per second, releasing enough energy to fracture, melt, and eject lunar rock.

That is why even relatively small objects can leave visible marks on the lunar surface.

Large Impacts Create Huge Basins

A larger impact releases much more energy and can excavate a much wider area.

The biggest collisions created enormous impact basins, some hundreds of kilometers across. These ancient structures are among the largest scars preserved on the Moon.

Why Don’t Moon Craters Disappear?

On Earth, wind, rain, rivers, glaciers, vegetation, volcanism, and plate tectonics constantly reshape the surface.

The Moon lacks most of these processes. Its surface still changes, mainly through later impacts and effects from the space environment, but the changes happen much more slowly than on Earth.

The Moon Has Almost No Atmosphere

The Moon has an extremely thin exosphere, not a substantial atmosphere like Earth’s.

There is no weather system with strong winds and rain constantly wearing down crater walls. As a result, lunar craters can remain recognizable for extremely long periods.

There Is No Rain or Running Water

Liquid water does not flow across the Moon’s surface in the way it does on Earth.

On Earth, flowing water breaks down rock, carries sediment, and gradually reshapes landscapes. Without this widespread process, lunar craters can survive far longer.

The Moon Has No Earth-Like Plate Tectonics

Earth’s crust is continually moved and recycled by plate tectonics. This can bury or destroy ancient impact structures.

The Moon does not have Earth’s active plate-tectonic system. Its surface therefore preserves much more of its ancient history.

Why Does Earth Have Fewer Visible Craters?

Earth is actually a larger target for incoming objects, so its lower number of visible craters does not mean it has avoided impacts.

Instead, Earth is much better at hiding its impact scars.

Earth’s Atmosphere Stops Many Small Objects

When small meteoroids enter Earth’s atmosphere, many heat up and break apart before reaching the ground.

The Moon’s extremely thin exosphere provides almost no comparable protection. Objects that would break apart high in Earth’s atmosphere can reach the lunar surface and create impacts.

Large objects can still pass through Earth’s atmosphere and produce major craters, so the atmosphere does not prevent all impacts.

Earth’s Surface Is Constantly Changing

Earth’s surface is reshaped by erosion, sedimentation, glaciers, volcanic activity, and plate tectonics.

These processes can wear down a crater, bury it under younger material, or destroy it completely. NASA notes that even Earth’s preserved impact craters are far fewer than the evidence of ancient impacts would suggest because geological processes have removed much of the record.

Why Are Some Moon Craters Millions or Billions of Years Old?

A lunar crater can remain recognizable for an extremely long time because the Moon has few processes capable of completely removing it.

Later impacts can damage older craters, while tiny impacts gradually churn the surface. But compared with Earth, the lunar landscape changes slowly.

Ancient Craters Can Stay Visible

Older craters may become worn down or partly covered by later impacts.

When one crater overlaps another, scientists can determine which impact happened first. These relationships help them work out the relative ages of different parts of the lunar surface.

The Moon Preserves the Past

The Moon’s cratered surface provides a record of impacts that occurred long ago.

By studying these craters, scientists can investigate the history of the Moon and learn more about the collision history of the Solar System.

Does the Moon Still Get Hit by Space Rocks?

Yes. Meteoroids and other small objects continue to strike the Moon today.

Scientists have observed brief flashes from some lunar impacts. Smaller particles also constantly disturb the uppermost layer of lunar soil, a process known as impact gardening.

So crater formation is not only an ancient process. It is still happening, although large impacts are much less common.

Why Are There Different Types and Sizes of Moon Craters?

Not every impact produces the same crater. The final shape depends partly on the object’s size, speed, impact angle, and the surface it strikes.

Small impacts can create simple pits, while larger impacts can produce complex craters with features such as central peaks or, in the largest cases, multiple rings.

Small Impacts Make Small Craters

Tiny meteoroids and particles can leave small pits across the lunar surface.

Over billions of years, countless impacts have added to the Moon’s heavily marked appearance.

Large Impacts Make Complex Craters

Large collisions can excavate much more material and create wider, more complicated structures.

Some of the largest impacts formed basins hundreds of kilometers across, reshaping enormous areas of the lunar surface.

Why Are Moon Craters Important to Scientists?

Craters are more than marks on the Moon. They provide clues about the history of its surface and the objects that have struck it.

Scientists study crater size, distribution, overlapping relationships, and the materials around them to understand how different parts of the Moon have changed over time.

Because Earth’s surface has erased much of its ancient impact record, the Moon provides a particularly useful record of the Solar System’s impact history.