Life is tough for a humble grain of dirt on the surface of the Moon. It’s peppered with cosmic rays, exposed to solar flares, and battered by micrometeorites–shattered, vaporized and re-condensed countless times over the billions of years. Adding insult to injury, Earthlings want to strip it down to oxygen and other elements for “in situ resource utilization,” or ISRU, the process of living off the land when NASA returns to the Moon in the not-so-distant future.
But, as Robert Heinlein famously observed, “the Moon is a harsh mistress.” Living with moondust and striping it down may be trickier than anyone supposes.
To find out how tricky, researchers would like to test their ideas for ISRU and their designs for lunar rovers on real lunar soil before astronauts return to the Moon. But there’s a problem:
“We don’t have enough real moondust to go around,” says Larry Taylor, director of Planetary Geosciences Institute at the University of Tennessee in Knoxville. To run all the tests, “we need to make a well-qualified lunar simulant.” And not just a few bags will do. “We need tons of it, mainly for working on technologies for diggers and wheels and machinery on the surface,” adds David S. McKay, chief scientist for astrobiology at the Johnson Space Center (JSC).
Taylor and McKay are lead members of a small group of self-styled “lunatics” whose careers have focused on lunar soil and rocks. They are among several consultants to NASA’s Marshall Space Flight Center (MSFC), which manages the Lunar Regolith Simulant Development Program.
Carole McLemore is the program manager at Marshall. Back in the 1990s, she explains, researchers used a lunar simulant called JSC-1 developed at JSC. But “there is no more JSC-1 available.” So, to get started, researchers at Marshall are working with the Astromaterials Research and Exploration Science office at Johnson to create a replica of the JSC-1 simulant: JSC-1A. It comes in three types based on grain size (fine, medium and coarse). MSFC has also begun work on more demanding simulants representing various locations on the Moon.
Until the Apollo astronauts brought lunar soil samples to Earth during 1969-72, the belief was that the Moon’s dry, airless environment left the soil largely undisturbed. Reality is much harsher.
Micrometeorites, many smaller than a pencil point, constantly rain onto the surface at up to 100,000 km/hr (about 62,000 mph), chipping off materials or forming microscopic impact craters. Some melt the soil and vaporize and re-condense as glassy coats on other specks of dust. Impacts weld debris into “agglutinates.” Complicated interactions with the solar wind convert iron in the soil into myriads of “nano-phase” metallic iron grains just a few nanometers wide.