Lunar Regolith: A Surface Built by Impacts

The Moon has no soil in the biological sense. Its surface is covered by regolith: a layer of broken rock, mineral fragments, glass, and dust produced largely by billions of years of impacts.

This loose material records both destruction and history.

Gardening Without Life

Meteoroids strike the Moon at high speed because there is almost no atmosphere to slow them. Large impacts excavate craters and spread ejecta. Tiny impacts continually crush and melt surface grains.

Scientists call this repeated mixing “impact gardening.” Older material can be buried, exposed again, and mixed with fragments from distant craters.

Some grains contain glass formed by the heat of impact. Others develop microscopic rims through exposure to the solar wind and micrometeorites. These changes are known as space weathering.

Why Regolith Matters

Regolith affects how the lunar surface reflects light, so remote-sensing data must account for weathering and grain properties. A fresh crater may expose brighter material that darkens over time.

The layer also matters for exploration. Fine dust can cling to equipment, abrade surfaces, and affect seals. The strength and depth of regolith influence landing and construction.

At the same time, regolith contains resources. Some regions may preserve oxygen bound in minerals, useful elements, or water ice mixed with soil in permanently shadowed polar areas.

A Complicated Archive

A lunar sample does not always represent the bedrock directly beneath it. Impacts can transport fragments across the surface, sometimes over great distances.

Interpreting regolith therefore requires provenance: where a grain came from, how long it was exposed, and how many times it was reworked.

The Moon's surface may look inactive, but its upper layer has been continuously processed by impacts and radiation. Lunar regolith is both an engineering challenge and a geological archive—one made not by rivers or organisms, but by the long exposure of an airless world to space.