Mining the Moon vs. Asteroids Near Earth

There is a longstanding debate as to whether it is better to mine the Moon or asteroids first, with professional opinions split so that there is nothing near a consensus on the matter, being closer to 50-50 rather than one extreme or the other.

After the discovery of water ice at the lunar poles, the Moon became more attractive to many people, but that didn't swing the vote a lot.

There are multiple factors to consider, whereby how much weight should be given to each is up for debate:

• Understanding of composition -- The Moon is better understood in terms of mineralogy, due to the Apollo samples and many recent orbiter probes, thereby giving more information as a basis for design of equipment, and minimizing risk. As of early 2012, we don't know much at all about the composition of target asteroids near Earth. Asteroids offer a greater diversity of ores, and that risk can be reduced by future spectroscopic analysis and probes. Right now, the Moon has the advantage, but that advantage may reverse as we explore the asteroids.

• Fuel propellant costs -- The Moon requires fuel for landing and takeoff, which means a larger payload launched from Earth, more fuel propellant manufactured on the Moon for the return cargo, and a little bit of risk in landing. Some target asteroids have a great advantage here, whereby a smaller mission could potentially bring back a lot more material. Moon advocates point out that the extra Earth launch cost is just a slightly greater expense in the overall economics of their project, all considered, and that docking multiple payloads at a space station to deploy to the Moon is not a significant issue, relatively speaking. (In the longer term, electromagnetic launch catapult, aka a "mass driver", can take away much of the advantage of asteroids.)

• Transit times -- "Time is money." The Moon is always nearby. Asteroids offer windows of time when they are most easily accessible for an outgoing mission, and when materials can be most economically returned to Earth. Some asteroid advocates call for a hit and run job, returning a raw chunk of an asteroid (if not the whole thing) or else processing the material very quickly.

• Teleoperation -- The Moon has a communications time delay of just 2.5 seconds (speed of light) so that teleoperating equipment from Earth is a lot less difficult. For asteroids near Earth, it will be much longer, minutes. Advocates of asteroid mining tend to be development optimists betting on advanced automation and artificial intelligence reducing this issue to relative insignificance.

• Materials processing environment -- Asteroids offer zero gravity and microgravity materials processing options. Of course, if a stronger gravity is desired, then a centrifuge can be used. For the Moon, it's minimum 1/6th g. Giant solar ovens with easy solar tracking can be easily deployed in orbit around an asteroid. Not so easy on the surface of the Moon. However, the Moon's gravity allows us to apply and test equipment variations from Earth mining relatively quickly.

• Solar power -- At an asteroid, solar electric power is continuous. On the Moon, the only places with continuous solar power are not necessarily in proximity to where you want to do mining and materials processing. The top of the rims of some polar craters receive continuous sunlight. That is like the top of a mountain -- not easy to get to and would require power beaming or long cabling. The option of nighttime power storage adds equipment plus increases the daytime power generation needs. Nuclear power is an option but introduces some complications, while requiring substitute methods instead of solar ovens (of which there are many alternatives).

• Quality of ore -- Asteroids offer more potential diversity of material inputs, such as high grade ores for platinum group metals. However, the lunar poles definitely have valuable water ice, as well as metal granules, and many interesting "ores" which are sufficiently valuable for things in bulk demand. (The lunar ice is extremely cold, but that is not such a big technical problem, contrary to what some people express.)

• Emergency delays -- If equipment breaks beyond repair, the Moon is just a few days away for a resupply. For asteroids, it could be months.

There are additional differences, but the above are the most significant ones for a nearterm mission.

What will be most important is which company can start generating substantial cash flow or even profits first.

We could look at longer term issues. For example, when a mass driver catapult inevitably comes into existence on the Moon, then an orbital refinery can process lunar materials as well as asteroidal materials, in a scenario where unprocessed or preprocessed materials are returned to Earth orbit, thereby benefiting a lunar investment and colony establishment. However, if asteroids become more profitable first, then it may be an asteroid mining company which has the most resources to develop the Moon.

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