Having written before on the ethics of asteroid mining, I thought I would return to this subject and address an additional moral concern, namely the potential dangers of asteroid (and comet) mining. My concern here is not with the dangers to the miners (though that is obviously a matter of concern) but with dangers to the rest of us.
While the mining of asteroids and comets is currently the stuff of science fiction, such mining is certainly possible and might even prove to be economically viable. One factor worth considering is the high cost of getting material into space from earth. Given this cost, constructing things in space using material mined in space might be cost effective. As such, we might someday see satellites built right in space from material harvested from asteroids. It is also worth considering that the cost of mining materials in space and shipping them to earth might also be low enough that space mining for this purpose would be viable. If the material is expensive to mine or has limited availability on earth, then space mining could thus be viable or even necessary.
If material mined in space is to be used on earth, the obvious problem is how to get the material to the surface safely and as cheaply as possible. One approach is to move an asteroid close to the earth to facilitate mining and transportation—it might be more efficient to move the asteroid rather than send mining vessels back and forth. One obvious moral concern about moving an asteroid close to earth is that something could go wrong and the asteroid could strike the earth, perhaps in a populated area. Another obvious concern is that the asteroid could be intentionally used as a weapon—perhaps by a state or by non-state actors (such as terrorists). An asteroid could do considerable damage and would provide a “clean kill”, that is it could do a lot of damage without radioactive fallout or chemical or biological residue. An asteroid might even “accidentally on purpose” be dropped on a target, thus allowing the attacker to claim that it was an accident (something harder to do when using actual weapons).
Given the dangers posed by moving asteroids into earth orbit, this is clearly something that would need to be carefully regulated. Of course, given humanity’s track record accidents and intentional misuse are guaranteed.
Another matter of concern is the transport of material from space to earth. The obvious approach is to ship material to the surface using some sort of vehicle, perhaps constructed in orbit from materials mined in space. Such a vehicle could be relatively simple—after all, it would not need a crew and would just have to ensure that the cargo landed in roughly the right area. Another approach would be to just drop material from orbit—perhaps by surrounding valuable materials with materials intended to ablate during the landing and with a parachute system for some basic braking.
The obvious concern is the danger posed by such transport methods. While such vehicles or rock-drops would not do the sort of damage that an asteroid would, if one crashed hard into a densely populated area (intentionally or accidentally) it could do considerable damage. While such crashes will almost certainly occur, there does seem to be a clear moral obligation to try to minimize the chances of such crashes. The obvious problem is that such safety matters would tend to increase cost and decrease convenience. For example, having the landing zones in unpopulated areas would reduce the risk of a crash into an urban area, but would involve the need to transport the materials from these areas to places where it can be processed (unless the processing plants are built in the zone). As another example, payload sizes might be limited to reduce the damage done by crashes. As a final example, the vessels or drop-rocks might be required to have safety systems, such as backup parachutes. Given that people will cut costs and corners and suffer lapses of attention, accidents are probably inevitable. But they should be made less likely by developing rational regulations. Also of concern is the fact that the vessels and drop-rocks could be used as weapons (as a rule, any technology that can be used to kill people will be used to kill people). As such, there will need to be safeguards against this. It would, for example, be rather bad if terrorist were able to get control of the drop system and start dropping vessels or drop-rocks onto a city.
Despite the risks, if there is profit to be made in mining space, it will almost certainly be done. Given that the resources on earth are clearly limited, access to the bounty of the solar system could be good for (almost) everyone. It could also be another step form humanity away from earth and towards the stars.