When astronauts eventually walk on the moon again, they might thank a scientist named Jérôme Juilleret for helping them figure out where to step. Juilleret, a soil researcher in Luxembourg, has spent years studying dirt — but not the kind you find in a garden. He is mapping the soil of the moon.
Most of what scientists know about lunar soil comes from satellite images taken from far away. These views from space cannot show the details needed to choose the best landing spots for building, mining, or growing food. "Pedology has spent more than a century learning how to classify and map soils on Earth," said Juilleret, an engineer in soil sciences and hydrology at the Luxembourg Institute of Science and Technology. "We believe this expertise can now help guide the next era of lunar exploration."
In a new study published in the Soil Science Society of America Journal, Juilleret and his team propose the first-ever classification system for lunar soils. They call this new field "planetary pedology" — essentially, the science of naming and sorting soils on other worlds. It works like a filing system: by categorizing soil types, scientists can compare different areas of the moon and pick the right spot for whatever they need to do there.
The idea might sound strange. People have long thought of moon dirt as just powdery rock dust with nothing interesting going on. But scientists now realize lunar soil has real structure, shaped over billions of years by impacts from tiny meteors and chemistry caused by sunlight. It is different from Earth soil — it has no worms, no roots, no rotting leaves — but it is not featureless either.
To test their system, the researchers studied a cylinder of moon dirt collected by Apollo 15 astronauts back in 1971. Using their new classification framework, they identified seven distinct layers buried deep underground, each one recording a different stage in the moon's history. It is a bit like reading tree rings, but for the moon.
The timing matters. Multiple countries and private companies are racing to establish a lasting human presence on the moon. If people are going to live there for months or years, they will need to build shelters, dig for ice, and perhaps even grow food — all of which requires understanding the ground beneath them. A standard soil map could tell astronauts, "Dig here for water, build there, avoid this spot entirely."
Juilleret's work suggests that knowledge earned studying Earth soils for over a century can travel with us to the stars. As humanity looks ahead to sustainable life beyond our planet, his lunar filing cabinet may become an essential tool.