Quoting from NASA warned plan to send humans to Mars may fail news article:
The Obama administration is opposed to another moon landing, saying such a mission would be too costly. It wants instead to focus on capturing an asteroid and placing it into the Moon's orbit for future exploration.
How useful is "placing an asteroid in lunar orbit"? What are implications as a function of research?
There are entities that hope to mine asteroids, Planetary Resources and Deep Space Industries.
The proposed Asteroid Retrieval Mission is based upon the Keck Report, a paper outlining how a small Near Earth Asteroid (NEA) could be parked in lunar orbit.
Co-authors of the Keck Report include
And a long list of other prominent scientists and engineers whose focus is near earth asteroids.
Many of the co-authors of the Keck Report are also on the staff of Planetary Resources or Deep Space Industries.
Developing a retrieval vehicle with powerful Solar Electric Propulsion (SEP) engines would be a big step towards making asteroid mining plausible. Robust SEP might also be helpful for ferrying massive payloads from earth orbit to lunar orbit, so the technology would also make establishing a lunar base more doable.
Why park an asteroid in lunar orbit? Why not mine it in its heliocentric orbit?
Early asteroid mining will be a process of trial and error. So establishing infra structure will require multiple trips. Trip times to an NEA would be months to a better part of a year. The most accessible asteroids with earth like orbits also have very rare launch windows, on the order of years and decades apart. Light lag latency to a NEA in heliocentric orbit can be 10s of minutes. Since signal strength falls with inverse square of distance.
Let's compare that to an asteroid in lunar orbit. Trips times are less than a week. Launch windows from a given low earth orbit occur each two weeks. Light lag latency is about 3 seconds. Telerobots at ~1 lunar distance can enjoy high bandwidth.
For these reasons lunar orbit is a much better place to develop the fledgling asteroid mining technology.
Placing an asteroid in lunar orbit would be very useful.
The Asteroid Retrieval Mission (ARM) is most fundamentally critizied out of disappointment because that's what's left of the envisioned great crewed space mission of our lifetime. Instead of building a permanent lunar base or going to Mars or to a real asteroid, we'll just make a trip back to lunar orbit. That does not inspire. Russian, Chinese and even private entities might do that before ARM completes. This priority will make NASA lose its outstanding place in the imagination of human kind and turn it into an outcompeted second rate space flight organization with recruitment problems.
Even as an asteroid mining technology demonstration it is flawed. Such tiny meteoroids are out of the question when it comes to mining. And Solar Electric Propulsion (SEP) cannot be used to move real asteroids with thousands times the mass.
The science of it is also questionable. Asteroids are likely very diverse. They may have formed in different parts of the solar system at different times in different ways. Some primordial, others more recent impact fragments. A close look at a sample of one will not say much at all about the typical asteroid. Especially since meteoroid sized objects very well may be systematically different from real asteroids. Maybe they are mostly rubble piles which separate easily.
The meteoroid size and propulsion technology is also irrelevant for planetary defence. The Chelyabinsk meteor was larger than what ARM plans to go for.
The political explanation of why the ARM mission exists, seems more logical than any rationale based on science or space economy development. ARM seems to be a political way to motivate the continuation of already ongoing projects like the SLS, Orion and SEP. They all have good potential uses, but the combination is strained and the usefulness limited to keeping those projects financed. Many critics are convinced that ARM will actually never happen, that it will soon be canceled.
Long term, an asteroid-to-orbit mission has several benefits:
Capture of an asteroid has several geopolitical considerations that give it value, ones which don't require manned missions by anyone.
The proven ability to move asteroids into orbit, especially lunar-coorbit (LaGrange points) or Lunar orbit, would establish definitively a level of fine control over asteroid movement. That level of fine control is a requisite for use of asteroids as weapons of mass destruction, and is directly on par with orbital insertion.
This is undoubtedly a part of the considerations - such a practical capability is bidirectional - if you can put one into stable orbit, you can also crash it, and also send it away from Earth. In other words, by proving you can make a successful insertion, you prove you can prevent one, as well.
The commercial applications, much as with the Apollo program, are a justification, but are probably not the root for the program. (Apollo established that the US could in fact deliver a missile payload anywhere desired within cislunar space.) The mining value of a nickel-iron asteroid as base metal is not worth the effort - it would cost more to recover the metal than the metal is worth. One that has significant other metals would be financially valuable, but the programmatic costs and landing costs may not be viable long term. Planetary Resources thinks they can manage it and make money - but if they had secure numbers, we'd see backers lining up to privately fund it. The risk is too high. (Further, the geopolitical aspects make it impractical to pull it off without it looking like a threat.)
The scientific value of an asteroid to orbit is immense - on par with putting men on the moon, but only slightly so. In addition to the mission itself and its science value as a near-system trans-lunar mission, there is the benefit of it being a platform for a much more radiation-proofed space platform, which would enable truly long-term science missions in microgravity.
The combination makes the asteroid to orbit overall a higher priority for politicians than the pure science of further lunar missions or the science adventure of Mars.
