Asteroids and the Human Near Future in Space

(Image: ESA)

If news reports from earlier this year are to be believed, asteroids are high on the list of celestial bodies to be explored – and manipulated. On May 13th, The Telegraph revealed that British astronaut Tim Peake was going to be trained by NASA for an asteroid surface mission. Only weeks earlier, on April 24th, the American company Planetary Resources announced its plans to invest in asteroid mining technology. In the background the impressive exploration data from NASA’s Dawn mission to the asteroid belt trickles in, mainly concerning protoplanets Vesta and Ceres.

It’s clear that at least some of the professional and public focus concerning space exploration has shifted away from Mars and the Moon towards the (mostly) smaller objects in the solar system. Space between Mars and Jupiter, for example, is filled – relatively speaking – with asteroids, coalesced matter that was prevented by Jupiter’s gravitational influences from ever forming anything resembling a real planet. It’s easy to see why asteroids would be prone to a surge in interest as well: they represent something of a hidden side to the Solar System in the public eye, which has for centuries been focused mainly on the Planets proper. That these latter have some sort of mythological status even among secular people was evidenced by the outrage over Pluto’s downgrading to ‘dwarf planet’ status in 2006.

As the plans presented by Planetary Resources indicate, asteroids – and in this case particularly those ~9000 that are close to Earth, rather than in the main belt –  can be considered a source of untapped resources that can be harvested, particularly for use in space missions. In terms of profit, it seems obvious that the company is interested in rare metals such as platinum, as put forward in WIRED. One other precious resource that will be less obvious to most Earth-dwellers is water. It takes tremendous amounts of energy to launch large quantities of water from Earth into space, so if long-term manned space missions could make a pit stop for water somewhere in Earth orbit at a station filled with asteroid water, that would save a lot of effort. Not to mention the fact that water can be used to make rocket fuel.

More deeply rooted in public consciousness is perhaps the concept of the asteroid as something that can potentially crash into the Earth, with apocalyptic consequences. Indeed, this has happened before (e.g. the dinosaur extinction), and it is likely to happen again at some point in the future, though it is difficult to indicate when – I will return to this point below. This idea has been picked up in fiction as well, such as in Arthur C. Clarke‘s 1993 novel The Hammer of God, which I’ve yet to read, and more famously in the 1998 films Deep Impact and Armageddon. Why both movies about exactly the same occurrence were made simultaneously is somewhat of a mystery, but both of them firmly settled the idea of the potential dangers of asteroids in our minds.

Part of the future training missions concerning asteroids may focus on developing the technology to deflect asteroids from their trajectories, either to prevent them from hitting Earth, or instead to bring them closer to Earth for easier mining. Granted that it will be possible to do this reasonably accurately in the future, this raises some ethical issues that we, mankind, would do well to consider.

In his book Pale Blue Dot: A Vision of the Human Future in Space, Carl Sagan devotes a chapter to asteroids. Based on geological data, we may surmise that roughly once every million years, Earth is hit by an asteroid large enough to cause global catastrophe. Smaller impacts that can devastate smaller areas of the planet like cities or countries happen much more frequently, and Sagan estimates that the world is hit by an asteroid with the impact force equivalent to that of a large nuclear bomb once every few hundred years. Reason enough to start thinking of ways to prepare for such an event, he says, and judging by what has happened since his plea has not fallen on deaf ears.

The problem, however, is that the technology we can use to protect the earth from asteroids could also be used as a weapon:

The problem, Steven Ostro of JPL and I have suggested, is that if you can reliably deflect a threatening worldlet so it does not collide with the Earth, you can also reliably deflect a harmless worldlet so it does collide with the Earth. [...] The technology required [...] all exist today. (p. 255-257)

Sagan is on to something here, applying his trademark skepticism to asteroid-deflection technology, and wondering if this technology will be safe in our hands. Can we be sure that this technology won’t be used by some nation or other group (a corporation?) to inflict targeted devastation on some other? It is not unthinkable that this technology could spark a new Cold War, or worse:

If we develop and deploy this technology, it may do us in. If we don’t, some asteroid or comet may do us in. The resolution of the dilemma hinges, I think, on the fact that the likely timescales of the two dangers are very different – short for the former, long for the latter.
Since the danger of misusing deflection technology seems so much greater than the danger of imminent impact, we can afford to wait, take precautions, rebuild political institutions – for decades certainly, probably centuries. If we play our cards right and are not unlucky, we can pace what we do up there by what progress we’re making down here. The two are in any case deeply connected. (p. 262-264)

Whether one agrees with Sagan’s assessment of the human proclivity to violence or not is a matter of debate. Personally, I’m inclined to agree, and regardless, it might not be a risk we want to take. Surely it couldn’t hurt to take his advice into account, and make sure that there are political institutions and treaties in place that ensure the non-violent use of deflection technology and the monitoring of this use, before we start making serious work of it. It would be a damn shame if mankind proves its critics right be destroying itself before something else gets the chance to do so.

Finally, I wish to briefly remark on what is perhaps a less pressing ethical issue, but an interesting one nonetheless. It concerns our attitude towards what lies beyond our own planet. Though I see little practical harm in extracting resources from asteroids, we must be mindful of what it means to start exploiting (in the relatively neutral sense of the word) outer space, so soon after we’ve started exploring. Matters of sustainability come to mind, but it’s also interesting to daydream about contact with other lifeforms that might be out there. Once we encounter them, can we still go on exploiting the resources that lie within their sphere of influence? This, of course, leads us to another blockbuster movie, James Cameron’s Avatar (2009), which tackles precisely these moral dilemmas. Perhaps that is one of the reasons why Cameron is one of the consultants on the board of Planetary Resources, Inc. – so he can keep an eye on them.


  • Carl Sagan (1994 [1997]). Pale Blue Dot: A Vision of the Human Future in Space. New York: Ballantine.
  • qwallath

    “Sunlight has a subtle effect on asteroids, pushing them around ever so slightly. This Yarkovsky effect, as it’s called, is caused when sunlight is absorbed and re-emitted as heat. Now scientists have measured the precise change in an asteroid’s orbit caused by this.”

  • qwallath

    And the technology is certainly developing: (2002)

    “Impacting at hypervelocity, an asteroid struck the Earth approximately 65 million years ago in the Yucatan Peninsula area. This triggered the extinction of almost 70% of the species of life on Earth including the dinosaurs. Other impacts prior to this one have caused even greater extinctions. Preventing collisions with the Earth by hypervelocity asteroids, meteoroids, and comets is the most important immediate space challenge facing human civilization. This is the Impact Imperative. We now believe that while there are about 2000 earth orbit crossing rocks greater than 1 kilometer in diameter, there may be as many as 200,000 or more objects in the 100 m size range. Can anything be done about this fundamental existence question facing our civilization? The answer is a resounding yes! By using an intelligent combination of Earth and space based sensors coupled with an infra‐structure of high‐energy laser stations and other secondary mitigation options, we can deflect inbound asteroids, meteoroids, and comets and prevent them from striking the Earth. This can be accomplished by irradiating the surface of an inbound rock with sufficiently intense pulses so that ablation occurs. This ablation acts as a small rocket incrementally changing the shape of the rock’s orbit around the Sun. One‐kilometer size rocks can be moved sufficiently in about a month while smaller rocks may be moved in a shorter time span. © 2003 American Institute of Physics”