When we look up at the Moon, it’s impossible not to notice all those scars — craters covering almost every visible surface. Compare that to Earth, where you have to search pretty hard to find an impact crater, and it raises a natural question: why is the Moon covered in craters, but Earth isn’t?
The answer lies in how active — or inactive — the two worlds are.
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The Moon: A Time Capsule of Violence
The Moon has no atmosphere. That means meteoroids don’t burn up like they do on Earth; they slam right into the surface, forming a crater almost every time.
And because there’s no wind, rain, rivers, or glaciers, once a crater is formed, it stays there — often for billions of years.
The Moon’s surface is like a giant museum of solar system history, with no janitor to sweep up the broken exhibits.
On top of that, the Moon has no plate tectonics. It doesn’t have massive crustal plates drifting around, subducting old surfaces and building new ones like Earth does.
In short: once something happens to the Moon’s surface, nothing erases it.
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Earth: The Restless World
Earth, by comparison, is a living, breathing planet.
• Our atmosphere burns up most small meteors before they even reach the ground.
• Rivers carve valleys, winds sculpt deserts, glaciers bulldoze landscapes.
• Plate tectonics recycle the crust itself, burying old impacts under new mountains and oceans.
In fact, Earth’s surface is so dynamic that only about 190 confirmed impact craters have been found worldwide — and many of those are worn down almost beyond recognition.
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The Moon’s “Seas” — Evidence of Ancient Change
While the Moon looks frozen today, it wasn’t always so quiet.
Billions of years ago, giant asteroid impacts blasted enormous basins into the surface.
Later, volcanic eruptions filled many of these basins with dark, iron-rich lava, creating the familiar dark patches we call mares (Latin for “seas”).
Sea of Tranquility — where Apollo 11 landed — is one of the most famous examples.
These ancient floods were the Moon’s last major act of surface change.
Since then, it’s been mostly the slow peppering of tiny impacts and the occasional mild moonquake — nothing Earth would even notice.
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Analogy: A Car vs. A Snail
If you think in terms of geological time, Earth’s surface changes like a sports car tearing down a highway, while the Moon moves like a snail inching along the gravel shoulder.
• On Earth, entire mountain ranges can rise and erode away in the time it takes the Moon to accumulate a thin layer of dust.
In other words: the Moon did change — but compared to Earth, it’s almost completely frozen in time.
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Fun Fact: The Moon is Still Being Hit!
Even though the major bombardment of the Moon ended billions of years ago, it still gets hit by small meteoroids all the time — about one detectable impact every week!
Some of these impacts are even bright enough to spot from Earth using backyard telescopes, especially during meteor showers like the Geminids or Leonids.
NASA even runs programs to monitor these flashes, giving amateur astronomers a chance to see the solar system’s ongoing activity live!
What About Impacts Today? Could They Move the Moon?
You might wonder: if the Moon keeps getting hit by meteors, could enough impacts eventually knock it off course?
Short answer: Nope.
Today’s impacts are tiny — like tossing BB pellets at a freight train.
Even a 10-ton rock slamming into the Moon barely registers against its mass of 7.35 × 10²² kilograms.
For fun, we crunched the numbers:
• To change the Moon’s orbit by just 1%, you would need to hit it with an asteroid about 2900 kilometers wide — that’s bigger than Pluto!
• Basically, you’d need to crash another small planet into it to make a noticeable difference.
So unless you’ve got a spare planet handy (and a good insurance policy), the Moon’s orbit isn’t going anywhere.
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Final Thought
Next time you look up at the Moon and see its cratered face, remember: you’re looking at a window into the ancient solar system, a frozen moment in time while Earth below keeps rushing forward at highway speed.
And if you happen to hear a faint tap-tap-tap… relax. It’s just another BB pellet hitting the freight train.
