Until the Apollo astronauts brought samples of lunar material to Earth during 196£-72, scientists believed that the Moon's surface was largely undisturbed, given its dry, airless environment. Examination of the samples has shown otherwise. Micrometeorites, many smaller than a pencil point, constantly rain onto the Moon at up to 100,000 kilometers per hour, chipping materials or forming microscopic craters. Some melt the soil and vaporize and recondense as glassy coats on other specks of dust. Impacts weld debris into lumps of heterogeneous matter called "agglutinates." Complicated interactions with solar particle streams convert iron into myriads of microscopic iron grains. The regdith—pebbles, sand, and dust-from these erosion processes blankets the Moon. Much of the top layer consists of a complex abrasive dust of microscopic glass shards that can grind machinery and sealing devices and damage human lungs.
The Apollo specimens held by the United States are doled out in ultra-small samples to scientists who demonstrate that nothing else will suffice for high-value experiments. Renewed interest In lunar exploration in the late 1980s meant that materials designed to simulate lunar regolith—simulants—were needed for research to develop schemes for lunar building and procedures for extracting elements such as oxygen found abundantly in regolith. That led to the development of JSC-1 in 1993, made of volcanic cinder cone from a quarry in Arizona in the U.S. The more than 22 metric tons made was in high demand. Efforts are now afoot to manufacture 16 metric tons of JSC-1 A, with 1 ton of fine grains, 14 tons of moderately fine, and 1 ton of coarse.
The reason cited in the passage for developing a few root simulants (see highlighting) is
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