When Neil Armstrong took “one giant leap for mankind” onto the surface of the moon in 1969, his booted foot sank into a layer of fine gray dust, leaving an imprint that would become the subject of one of the most famous photographs in history. Scientists called the dust lunar regolith, from the Greek rhegos for “blanket” and lithos for“stone.” Back then scientists regarded the regolith as simply part of the landscape, little more than the backdrop for the planting of the American flag.
No more. Lunar scientists have learned a lot about the moon since then. They’ve found that one of the biggest challenges to lunar settlement—as vexing as new rocketry or radiation—is how to live with regolith that covers virtually the entire lunar surface from a depth of7 feet to perhaps 100 feet or more. It includes everything from huge boulders to particles only a few nanometers in diameter, but most of it is a puree created by uncountable high-speed micrometeorites that have been crashing into the moon unimpeded by atmosphere for more than 3billion years. A handful of regolith consists of bits of stone,minerals, particles of glass created by the heat from the tiny impacts,and accretions of glass, minerals, and stone welded together.
Eons of melting, cooling, and agglomerating have transformed the glass particles in the regolith into a jagged-edged, abrasive powder that clings to anything it touches and packs together so densely that it becomes extremely hard to work on at any depth below four inches.
For those who would explore the moon—whether to train for exploring Mars, to mine resources, or to install high-precision observatories—regolith is a potentially crippling liability, an all-pervasive, pernicious threat to machinery and human tissue. After just three days of moonwalks, regolith threatened to grind the joints of the Apollo astronauts’ space suits to a halt, the same way rust crippled Dorothy’s Tin Man. Special sample cases built to hold the Apollo moon rocks lost their vacuum seals because of rims corrupted by dust. For a permanent lunar base, such mechanical failures could spell disaster.
Regolith can play havoc with hydraulics, freeze on-off switches, and turn ball bearings into Grape Nuts. When moon dust is disturbed, small particles float about, land, and glue themselves to everything.Regolith does not brush off easily, and breathing it can cause pulmonary fibrosis, the lunar equivalent of black lung. There is nothing like it on Earth. “Here you have geological processes that tend to sort and separate,” says geologist Douglas Rickman of NASA’s Marshall Space Flight Center. “On the moon you have meteorite impacts that mix everything together.”
