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© 2006 by Donald F. Robertson.
This article may be distributed at will, but only if it is not changed in any way, and only if the author's name, the copyright notice, the name of the journal it first appeared in, and this notice remain attached. In addition, this article may not be sold for money, or published for sale in any way, without the author's prior written permission.
This article originally appeared in International Space Review.
Donald F. Robertson
If the political and economic stars continue to line up, we’re off to the moon.
What do we do once we’re there?
Last month, we discussed commercial transportation to the moon. This time, we’ll look at what we might find there that is sufficiently valuable to use on site, or to transport for use elsewhere.
As on many trips, much of what we do is dependent on how long we stay. If we’re only going to dash in for six quick visits, like Apollo, there is little need for permanent infrastructure or to develop ways to live off the land. We’ll pack and go, and then return, full-stop.
If our stays expand to weeks or months, we can start “Lewis and Clark” class scientific traverses. For these expeditions, every resource that can be found locally is one that does not need to be shipped from Earth.
In space, everything is about mass, and its position in a “gravity well.” That rather archaic term refers to the field, or “well,” of gravity around an object like a planet.
If you are on Earth’s surface, you are at the bottom of Earth’s gravity well and it takes a large amount of energy -- and is therefore expensive -- to climb all the way up from the surface into deep space. If you are already orbiting at a hundred-thousand kilometers, you are high in the gravity well (as well as having the momentum of your orbital motion) and it is easy -- and cheap -- to escape to interplanetary space.
Looking at it from another angle, if you are on the surface of a small body with a shallow gravity well -- e.g., Earth’s moon -- it is far easier and less expensive to escape to space than it is from the bottom of a deep gravity well like Earth’s.
An object’s financial value is not only based on its scarcity (e.g., diamonds or platinum), but also on its position and the difficulty of getting it useful location, and on how useful it is at that location. Best of all is a substance that is useful everywhere. Oil is valuable not because it is scarce (at least not yet), but because it is flexible enough to be used for a wide range of purposes at almost any location.
Considering all of the above, what might be valuable in space? We must ask three questions. How heavy is it, and how deep in a gravity well is it located, i.e., how difficult is it to get to a useful location? How useful is it in how many different places?
What is the heaviest thing needed for any space application -- from exploration, to science and applications satellites, to resource exploitation and trade? Without doubt, the answer is oxygen.
Oxygen is readily available on most objects with shallow gravity wells, including Earth’s moon.
Oxygen is needed everywhere by everyone and everything. Oxygen, either by itself or bound into a compound, is by far the heaviest part of any likely chemical rocket fuel. Rocket fuel will be needed for the first lunar flight to head back to Earth and for every one thereafter. Oxygen will be needed in Earth orbit to start the lunar-bound leg of each trip. It will also be needed to fly between points on the lunar surface, and eventually to launch rockets toward other destinations such as nearby asteroids or Mars.
Oxygen is also the heavy part of water and many other useful compounds. You need oxygen to breathe; you need water to wash, to grow food, to store power in fuel cells. Oxygen and / or water are needed in a hundred common chemical reactions.
Since it is so essential, and used so widely in so many ways, oxygen in space is worth a great deal more than its weight in gold. Oxygen may well be the “oil” of the future.
Being the heaviest item needed in quantity, does it make any sense to lift oxygen from the largest solid surfaced planet, with the deepest gravity well in the inner Solar System?
Oxygen is known to be common in lunar regolith, and it is believed to be easily extracted. It exists as oxides of titanium and iron combined into illmenite, and probably as water ice in always-shadowed polar craters.
A team of scientists from NASA Goddard and the Space Telescope Science Institute is using the Hubble Space Telescope to map the locations on the lunar surface where oxygen-bearing rocks are most concentrated, and to look for other useful resources. They calibrated a camera that sees ultraviolet light by observing the known surfaces at the Apollos-15 and -17 landing sites. Then, the telescope observed the geologically-complex surfaces at Aristachus crater and Schroter’s valley, extending the resource maps to areas that have never been explored. The observations were preliminary tests of using ultraviolet cameras to observe the moon: the forthcoming Lunar Reconnaissance Orbiter will map the entire moon with its ultraviolet camera.
According to NASA Goddard’s chief scientists, Jim Gavin, “Our initial findings support the potential existence of some unique varieties of oxygen-rich glassy soils in both the Aristachus and Apollo-17 regions [at Taurus Littrow]. They could be well-suited for visits . . . in efforts to live off the land on the moon,” said Gavin.
Gavins comment brings up another useful resource -- glass. Orange glass beads, probably from ancient lunar volcanoes, are found exposed on the surface at the Apollo-17 site, and probably elsewhere. If found in sufficient quantity, these could be gathered from the lunar surface, then melted with solar heat.
Glass is largely inert, making it an excellent container and a strong, air-tight barrier. Natural lunar glass could be used to hold everything from gases to water to scientific samples to food supplies. It could be applied to the insides of structures made from lunar cement, making them air tight.
The cement could be made from the powdered rock created by billions of years of impact “gardening.” This would be combined with water from the poles, or with water manufactured from lunar oxygen and imported hydrogen, to make concrete.
The glass beads also contain oxygen -- making them a secondary source for that valuable commodity -- and iron.
Earth’s moon is very depleted in both heavy elements and volatiles. Combined with its extremely low rate of geologic change, the moon is likely to have few native concentrated ores. The shattered metallic cores of large ancient asteroids are the ultimate source of some metals used on Earth, and similar objects will have fallen on the moon. Such resources are likely to be rare and widely scattered, but once found may well prove almost as valuable as oxygen.
Apollo-17 geologist Harrison Schmidt is a tireless advocate for mining helium-3 deposited in lunar rocks by the solar wind. This resource may someday be sufficiently valuable to a nuclear-fusion powered economy to justify export to Earth, but not in the immediate future relevant to NASA’s current plans to return to Earth’s moon.
Oxygen, glass, cement, and the odd heavy metal may seem like slim pickings. However, given oxygen’s high importance and mass, that resource alone may make the difference for an affordable lunar base.
Successfully extracting useful resources from an ancient, poor, and heavily-battered old world like Earth’s moon provides early practice for richer but more distant prizes -- the asteroids themselves.
Donald F. Robertson is a freelance space industry journalist based in San Francisco.
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