Most craters on the Moon formed when asteroids, comets, or smaller meteoroids struck the surface at high speed. Impacts blasted material outward and left rimmed depressions. The Moon preserves many old craters because it has virtually no weather or flowing water to erase them and much less active surface recycling than Earth.
A fast impact excavates the surface
An impactor releases energy when it hits the Moon. Rock and soil are crushed, melted, or thrown outward as ejecta. Crater shape depends on impact energy and lunar geology. Small craters are often simple bowls; larger impacts can create terraces, central peaks, or broad basins as the rim and floor collapse. [1]
Why the Moon preserves craters
On Earth, wind, water, vegetation, tectonics, and volcanism alter or bury many impact structures. The Moon lacks substantial weather and its surface changes slowly. Smaller impacts still modify it, but ancient marks remain visible for billions of years. [2]
What craters reveal
Scientists compare crater numbers and sizes to estimate the relative ages of surface regions. Crater counting works best with samples and other geological evidence; it is not a direct stopwatch because impact rates and resurfacing add uncertainty. Read why the Moon’s two sides differ and how ice can persist on Mercury.
Frequently asked questions
Frequently asked questions
Are all Moon craters impact craters?
Most familiar rimmed lunar craters are impact structures, though volcanic features also occur.
Why do some craters have bright rays?
Fresh impacts scatter bright material outward; the rays fade as space weathering alters the surface.
Are new craters still forming?
Yes. Small impacts continue, and spacecraft have observed new impact sites and flashes.
Sources and evidence
- NASA Science — Lunar Craters ↗
Explains impact formation, ejecta, and crater structure.
- NASA Space Place — Why Does the Moon Have Craters? ↗
Compares lunar crater preservation with Earth’s changing surface.
- NASA Science — Why Study Moon Craters? ↗
Explains crater counting and lunar history.
Sources consulted: 2026-10-18. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Initial editorial draft prepared 18 October 2026; claims are tied to linked sources and retain stated limitations.