Moon Miners' Manifesto

#3 March 1987

Essays in "M"

M IS FOR MARE, PLURAL MARIA ( MAH-ray, MAH-ri-a )

The large dark areas on the Moon, the so-called Lunar Seas, formed three to four billion years ago when most of the large impact basis filled with layers of a very low viscosity lava and cooled. Some such basins on the Farside of the Moon did not fill with lava and are called "Thassaloids" ( from the Greek word for sea).

While an initial Lunar Base might be built just about anywhere, once more extensive settlements are built, the maria are clearly preferable. The regolith, the loose surface material, composed of rock fragments and soil, which overlies consolidated bedrock, has a very variable thickness in the highlands, from zero to 30 meters. On the mare, however, the regolith has a more uniform depth of about 10 meters, which makes construction easier. While Lunar concrete relying on calcium rich highland soil and upported hydrogen will be a lot cheaper for initial base construction than pre-built modules brought from Earth, once a lot of construction is planned, even that method will be too costly. The only way to go is site-extrusion, building the structures from the fused soil on the site itself. Mare soils melt 200C ( 360F ) lower than highland soils and so will require significantly less energy either in fusing rammed soil or in making panels of cast basalt. The melt's lower viscosity will also help in some applications.

The levelness of the mare surface will also be an asset to laying out any extensive settlement. And importantly, the average atomic number and weight of mare soils, as compared to highland soils, makes them preferable for shielding against cosmic rays, etc.

But the best mare sites will be just "offshore" so to speak, so that highland soil, richer in aluminum and calcium, will also be available for manufacturing and processing. Finally, such a site will offer more scenic and recreational interest.

[Subsequent articles in later issues of MMM call for "coastal" sites, in the spirit of this last paragraph.]

M IS FOR MULTIPLE SITES:

One settlement a world does not make! Of course one must start with a single site, and it will be able to serve most of the initial needs. But no site has all the assets. Soils differ not only from highland ( or terrae ) to mare but also from mare to mare and even within a given mare. Different materials are available to the prospective processor or miner at such sites as crater and rille walls, the central peaks of some large craters, and the so-called dark mantle deposits.

Some polar areas might have permashade fields of frozen volatiles like ice and carbon oxides. Some sites will be especially scenic. Locations along the limb between nearside and farside "librate": the Earth will alternately be just above and just below the horizon -- anyone want to build the first Lunar Honeymoon Resort? An observatory dedicated to the Great Andromeda Galaxy, M31, could be built in the north, while a similar installation in the south could concentrate on the Magellanic Clouds. Farside would be best for observation of the Milky Way and for giant radio telescopes and SETI searches, etc.

M IS FOR MOUNDS:

The first impression anyone will have of a Lunar Settlement will be that of a complex of mounds, the two-four meter ( six-thirteen foot ) overburden of Lunar soil used as thermal insulation and cosmic ray shielding. The downward pressure of this much lunar soil per square inch is much less than the upward pressure of the air inside the habitat. So this blanket of soil does not present a stress upon the habitat(s). You can look at this blanket of dust as an analog of the blanket of air which protects us on Earth from the same hazards. In fact, if you could freeze out Earth's atmosphere, it would provide a light snowy blanket about 15 feet thick.

Contents of this issue of Moon Miners' Manifesto