The study of planetary rings led me in a roundabout way to the study of dirt. “Dirt” is actually the lay term, while the technical term is soil or dust, depending on whom you’re talking to. In the mid-1990′s Martin Taylor, then a graduate student, and I, then a post-doc, conceived of a simple experiment to study the collisions that take place in planetary rings. This experiment, dubbed COLLIDE (COLLisions Into Dust Experiment), flew on the space shuttle in 1998 and 2001. Ring particles bump into each other very slowly (typically less than 1 cm/s), and they have negligible gravity, so that’s why the experiments needed the microgravity environment of the space shuttle. The experiment consisted of shooting marble-sized projectiles into trays of special space dirt and seeing what happens.

This is where the connection to the Moon comes in. Astronauts tromping around on the lunar surface will be kicking up a lot of dirt – uh, dust. How much dust, and how fast it moves, depends on exactly the same physics studied by COLLIDE. That’s in part because the special space dirt we used was JSC-1, a standard pulverized volcanic rock that was used to simulate lunar dirt. A totally different line of research has also led me back to the lunar surface. My colleagues and I have been studying the dynamics of charged dust particles in the solar system, and the small particles on the lunar surface collect charge and can dance around above the surface in surprising ways. Studying this has been yet another use for that incredibly dark and dirty JSC-1 powder. This is a potential hazard for lunar astronauts, and a contaminant for lunar experiments. We have been studying this process and have a review paper coming out in Reviews of Geophysics soon.

Now that NASA is discussing a permanently manned lunar base, there is another need for this lunar simulant, as JSC-1 and other similar terrestrial materials are known. NASA’s plans for the lunar dirt are not limited to avoiding contamination, which are the kinds of problems are experiments address. They are also planning on building, excavating, and, more fancifully, drinking, breathing, and burning lunar dirt. While I’m not holding my breath in anticipation of extracting useable water or oxygen from the lunar regolith (the rocks and dirt on the surface), there is no question that there will be drilling, excavating, and other mass movements of material on the lunar surface in order to establish permanent lunar structures. The problem is there is no more JSC-1. NASA has been working to establish a plan for tons of a new lunar simulant to be tested so that engineers and scientists can test lunar construction techniques. One of the most surreal experiences I’ve had in my scientific career was attending a NASA-sponsored workshop on plans to deal with Moon dirt that was also attended by representatives from the Caterpillar company and the John Deere company.