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When you’re walking in the forest, what’s that stuff beneath your feet? Here on Earth, we call it dirt, or soil. Take a look at dirt under the microscope, and you’ll see a collection of particles of rock, sand, little critters, and organic matter. The surface of the Moon is covered with a fine powdery material that you might want to call dirt. But that’s the wrong term. There’s no organic material on the surface of the Moon, and so scientists call it lunar regolith instead.
The term regolith is any layer of material covering solid rock. It can be dust, soil and broken rock. Nearly the entire lunar surface is covered with regolith. Bedrock is only visible on the walls of very steep craters. The Moon regolith was formed over billions of years by constant meteorite impacts on the surface of the Moon. Scientists estimate that the lunar regolith extends down 4-5 meters in some places, and even as deep as 15 meters in the older highland areas.
You can also use the term “lunar soil” to describe the lunar regolith, but many argue that the term isn’t appropriate because the moon regolith doesn’t have any organic material in it at all.
When the plans were put together for the Apollo missions, when the first humans would walk on the surface of the Moon, some scientists were worried that the lunar regolith was too light and powdery to support the weight of the lunar lander. Instead of landing on the surface, they were worried that the lander would just sink down into it like a snowbank. Landings by robotic spacecraft showed that the lunar soil was firm enough to support a spacecraft, and the astronauts later explained that the surface of the Moon felt very firm.
As NASA is working on plans to send humans back to the Moon in the next decade, researchers are working to learn the best ways to work with the lunar regolith. Future colonists could mine minerals and even oxygen out of the lunar soil. Since real lunar regolith is hard to come by, you can purchase lunar regolith simulant, made here on Earth.
We’ve done several articles about the Moon’s regolith here on Universe Today. Here’s a way astronauts might be able to extract water from lunar regolith with simple kitchen appliances, and an article about NASA’s search for a lunar digger.
You can listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?