The next panel had two very good NASA speakers, both of who have been with the agency since the Apollo era if I’m remembering right: Larry Taylor and Wendell Mendell.
I really liked Larry’s talk, because he focused on how science can be used to enable lunar development. While pure science may be cool, applied science is critical. I’ve been studying lunar science as a hobby for a while, and I learned some rather exciting tidbits from his talk. One of the big things he dicussed was the effects of nanophase iron deposits on lunar regolith. As he explained later on in the day when I asked him, one of the working hypothesis for how these deposits came into existance was impact heating of the iron-oxide bearing ore in the presence of solar wind hydrogen. The solar wind hydrogen in that situation would reduce the iron oxide to pure nanophase iron. Apparently these nanoscopic particles of iron are embedded and on the surface of almost all regolith particles. While I had heard of unoxidized iron fines being a roughly 1% component of the regolith, and I had heard of the thin coating of nanophase iron on the surface of some regolith particles, I didn’t realize that it was as prevalent as he was suggesting, and I also didn’t realize that those nanophase particles actually exist even completely inside the regolith particles.
The practical upshot of this information, is that particles much smaller than 10 micrometers are actually magnetically succeptible. You can pick them up in 1g. Larry actually demonstrated this with a small tube filled with some sifted Apollo 17 regolith. This is a hugely important piece of knowledge for dust mitigation issues, since this means that the very particles most likely to cause damage are also the ones easiest to handle with this technique. My coworker Pierce was suggesting that strategically placing magnets in a manner similar to the way that sacrificial anodes are used in salt-water systems to avoid galvanic corrosion might do the trick. The proper utilization of that knowledge may be one of the keys that enables lunar development, as the dust issue is one of the major technical difficulties that must be overcome.
The other upshot of this information is even cooler. The dispersion of nanophase iron particles within what amounts to a glass or ceramic matrix causes the particles to have very high microwave coupling. As he put it, he put a sample of lunar soil in his microwave along with a cup of tea on the side. Within 39 seconds, and long before the tea had boiled, he had a puddle of molten regolith. That’s pretty impressive realizing that you need to heat it to 1300C in order to melt the stuff! I had heard some objections previously to microwave heating of regolith, due to the idea that since the stuff had such lousy thermoconductivity, hotspots would form, and getting even melting would be nearly impossible. However, if the prevelance of this nanophase iron is as common as Larry was suggesting, and if the microwave coupling doesn’t decrease with increasing regolith particle size, this could be another hugely important piece of knowledge. The ability to melt regolith with relatively low amounts of microwave power is likely going to be taken advantage of in many lunar construction techniques of the future.
Anyhow, there’s lots of interesting ideas that can be derived from this knowledge, but I’ll save that for another post on another day.
The other talk, by Dr Mendell wasn’t quite as exciting or new, but he also made some very good points. One of the points is that the lunar science guys are quite happy to do what he called “utilitarian” science instead of just pure science, because the utilitarian sort might actually get them funding! The other point he made is far more interesting in hindsight.
There’s been a lot of debate in the lunar science crowd over what the results from the Clementine and Lunar Prospector probes really mean. In the “pop science” arena, the supposition is usually that this increase in hydrogen density measured is in the form of ice that is stored in the extremely cold parts of permanently shaded craters. The other hypothesis is that this hydrogen is just solar wind hydrogen that is in a higher concentration due to less outgassing due to the much colder temperature. Wendell reminded us of the fact that the science is still out on this question, and that in fact the current data leans slightly more strongly toward the solar wind hydrogen hypothesis than the water ice hypothesis. The answer to this question may well have a major effect on how the poles are mined. If it is in the form of water ice, there are some interesting techniques that were discussed in a later session that can be used. If the hydrogen is just in the form of solar wind volatiles embedded in the regolith, completely different methods will need to be used to extract the stuff. Wendell said in his talk that the only sure way of actually settling the question will require a rover of some sort being sent into one of these cold-traps to find out for sure. Remote sensing just won’t cut it.
The interesting thing is that either way, the amount of hydrogen there is the same. If it is water ice from comets, there may also be traces of hydrocarbons. If it is solar wind hydrogen, then there may likely be increased concentrations of other solar wind volatiles. As it is, solar wind hydrogen is actually one of the hardest volatiles for the regolith to contain. It is one of the first gasses that will escape when a regolith sample is heated. If it is concentrated by the polar cold traps, the relative abundance of other volatiles (such as N2, CO2, Sulphur, etc) might be even higher. Not to mention the oft discussed Helium-3. Wendell didn’t actually make this last point, but it comes from inference. If that is really the case, it looks like either way there’s a strong chance that we’ll find large amounts of other critical volatiles like Carbon and Nitrogen. Whatever their source, this is definitely an interesting possibility.
Here’s an interesting thought: does anyone reading this know of a good way that we could verify via remote sensing if there are increased concentrations of any of the other common solar wind volatiles? Hydrogen is often found via neutron backscatter techniques, but are there techniques that can detect nitrogen or carbon? This could be important. Consider this my first bleg.
The key takeaway I got from this was that while science for science’s sake is often a lousy driver for any project, science properly applied may be critical for how we commercially develop the moon. Never underestimate a scientist with rational self-interest.
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