Geology · impact craters, Earth versus the Moon

A hundred times rarer

The Moon has 5,185 confirmed craters wider than 20 kilometres. Earth — thirteen times larger, and struck by meteoroids at a higher density per square kilometre — has only 52. The gap comes down to Earth's active geology, which erases the evidence of every impact within a few hundred million years.

52
confirmed craters on Earth, wider than 20 km (Earth Impact Database)
5,185
confirmed craters on the Moon, at the same size threshold or larger
2.229 Ga
age of Yarrabubba, the oldest confirmed impact crater on Earth
190
confirmed impact structures on Earth, of every size
Why they're missing

A planet hit harder, carrying fewer scars

Earth is bigger than the Moon and has stronger gravity. Through gravitational focusing — a heavy body pulls in meteoroids from angles a smaller body would miss — its surface takes impacts at roughly two to two-and-a-half times the density per square kilometre of the Moon's, according to the orbital dynamics studies used to calibrate crater-based dating across the Solar System. By that logic, Earth should carry more scars than its satellite.

Instead, it carries nearly a hundred times fewer confirmed craters over 20 kilometres wide. The explanation lies in the age of the surface each impact lands on. More than 70% of Earth is ocean, and the seafloor recycles through subduction in roughly 200 million years — younger than most of the large craters known on land. On the continents, wind, rain, ice and vegetation smooth impact features down over tens or hundreds of millions of years, and shifting tectonic plates bury or destroy what's left.

On the Moon, with no atmosphere, water or tectonic plates, a crater stays almost unchanged for billions of years. More than 99% of its surface is older than three billion years, while roughly 80% of Earth's surface is younger than 200 million years. The two bodies most likely received a similar number of large impacts relative to their surface area. Only one of them kept the record.

The Moon's craters read like a nearly complete diary. Earth's are the pages that happened to survive.

The comparison

52 against 5,185, at the same size cutoff

Both figures use the same threshold: confirmed craters at least 20 kilometres across. The bars below aren't drawn to a literal scale — Earth's bar is stretched so it stays visible — but the real ratio is close to 99.7 to one.

Earth
52
Moon
5,185
Instrument

Explorer: 70 craters with known coordinates

Where the evidence survived

The global database lists over 190 confirmed structures; the map below shows the 70 for which the Earth Impact Database also publishes exact coordinates. Drag the slider to see how many survive up to a given age, and filter by diameter. Tap a dot for details.

2.229 billion years ago

Tap a dot on the map for a crater's name, country, diameter and age.

70 craters from the database compiled after the Earth Impact Database (Planetary and Space Science Centre, University of New Brunswick), for which coordinates are published. The full list of 190+ confirmed structures includes many without exact coordinates, which don't appear on the map.
Records

Four points on the list

Sources

Where the numbers come from

The continents on the map use the simplified Natural Earth 110m coastline (public domain), in an equirectangular projection. Ages are given in millions of years before present, rounded to the central value published in the database where the source gives a range.
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