Colonizing the Asteroids and Comets of our Solar System

I am tormented by an everlasting itch for places remote. I love to sail forbidden seas.
— Herman Melville

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After humanity has transitioned to a Type 1, sustainable, planetary civilization, after we have “redesigned the surface of the Earth,” we will begin to colonize the solar system. There are many reasons to want to colonize the solar system. The first is that our solar system is very rich and plentiful in resources such as metals, rare metals, and water. The second reason is necessity: as Carl Sagan argued in Pale Blue Dot, catastrophic events such as asteroid impacts or nearby supernova, although unlikely in the short-term, become almost inevitable when considered in the long-term. Therefore, to ensure our long-term survival as a species, we must eventually colonize the solar system and beyond for, as Carl Sagan once said, “the most practical reason imaginable—staying alive.” But let’s start out by thinking about the first reason. Some argue that all of these interplanetary resources would be transported to our home planet for the benefit of all of Earth’s inhabitants. I personally hold a view which is contrary to most experts. I think that in an economic system based on sustaining dynamic equilibrium of Earthly resources, the basic needs of all earthlings could be met and sustained for billions of years using just the resources provided by the Earth. If this is true, then we’d only need to transport resources from interplanetary space to our home planet in the event of a major catastrophe. It is my personal view that interplanetary resources will be used almost entirely (if not, entirely) to support intrepid human explorers and settlers on other worlds in our solar system.

Certainly, the most enticing and abundant sources of resources are the inner-asteroid belt between Mars and Jupiter, the outer Kuiper asteroid belt which resides in the trans-plutonian depths of deep interplanetary space, and the marvelous Oort Cloud—a vast array of trillions of icy comets, “little denizens of the cosmos,” concentrically surrounding the entire solar system. The water, rock, and metals contained within these little worlds would be used to sustain a long-term, human presence on them. The water could be excavated using robotic probes and used to grow food hydroponically; and the metals and rocks could be used by 3D-printers to construct beautiful domes and underground infrastructure where human colonists or settlers would live.

An ambitious proposal forwarded to NASA involved turning an asteroid into a spaceship which could soar across interplanetary space and perhaps beyond—something long ago envisioned by Carl Sagan in his Pale Blue Dot. This ambition has been named Project Rama, the goal of which is to send a large spacecraft to an asteroid. This spacecraft would use the inner rock and materials inside of the asteroid (which, if we wanted to, could be used to hollow it out) as a propellant to move the asteroid across space. The researchers developed computer software which they called Rock Finder. Rock Finder uses a catalogue of all tracked and categorized near-Earth objects. You then tell Rock Finder what kind of asteroid you’re looking for and when you need it, and Rock Finder will plan a space mission for you. These researchers suggest using Rock Finder to locate asteroids rich in resources, then send the seed spacecraft over to one, then moving the asteroid to a more practically useful location. They suggest moving these asteroids to the Lagrange points in our solar system (which, if we could develope and mass produce a strong enough material, would be easily assessable by using a space elevator to launch spacecraft as this important 1975 paper\(^{[1]}\) and this paper\(^{[2]}\) have calculated using the laws and principles of classical mechanics). These Lagrange points are a kind of “solar parking lot” which remain fixed in location relative to the Earth.

                      Figure 1 (click to enlarge)

If we wish to ever send intrepid human explorers to the asteroids and comets in our solar system, there are a few challenges which must first be overcome. One of them is that we must build a, what I’ll call, “living quarters” inside of the spaceships—habitats which support all of Maslow’s hierarchy of needs which are necessary for humans to survive, to stay healthy, and to thrive. Such living quarters would contain a 3D-printer capable of 3D-printing food; they would also contain other appliances and equipment which are necessary to support human life. These living quarters would rotate at just the right angular velocity which would generate centrifugal forces (not too strong or too weak) that emulate the strength of Earth’s gravitational field—something which is very important given the dangers of humans being subjected to low-gravity for long periods of time. When such a ship lands on one of our solar system’s asteroids, we could turn it into a spaceship but we could also just land the ship on the asteroidal surface and cover it with rock and other materials\(^{1}\) which would protect the ship from micro-meteorites and cosmic rays. It wouldn’t be difficult to dig an immense hole and proceed to remove material from within the interior of the asteroid until the asteroid is hollowed out. Then, after that, an enormous cylinder could be constructed within the interior of the asteroid. Then, we could build an expansive habitat on the “inner surface” of the cylinder as in Figure 1.
By rotating this cylinder at just the right angular velocity, centrifugal forces would be generated within the asteroid’s interior. The forces would exert the same “pull” as that pull which we experience here on Earth. Designing and building the infrastructure along the inner surface would be a task which would be completed in a collaborative effort between scientists, engineers, and artists. In Figure 2 (which was taken from the magnificent short film, Wanderers, shown above) is a depiction of the infrastructure and human habitat along the inner surface of a rotating cylinder inside of a hollowed out asteroid. (In reality, if the asteroid was spun at an angular velocity which produced centripetal forces that resemble Earth’s gravity, the asteroid would rapidly disintegrate and fly apart. But by constructing a large cylinder which rotates at the right angular velocity, we would in fact be able to create a human habitat within the interior of an asteroid.) Asteroids are very tiny and produce very weak gravitational fields which do not exert much “pull.” This means that the tensile strength necessary for a tether to be used as a part of a space elevator is vastly less than that required on larger worlds such as the Earth. The enormous tensile strength required to build an Earth-based space elevator without the tether snapping is profoundly prohibitive: many speculate that, for this reason, it is not yet practical to build a space elevator here on Earth. But it is unanimous amongst scientists and engineers that constructing a space elevator on smaller worlds such as the Moon or an asteroid is entirely feasible. In Figure 2 and in the film, you can see a space elevator within the inner, asteroid, habitat. 

                                                                      Figure 2 - click to enlarge (Source)

"This shot shows the inside of the asteroid from the previous scene. Just as I wrote about that scene, this is a highly speculative vision of an impressive piece of human engineering - a concept that science fiction author Kim Stanley Robinson calls a "terraruim" in his novel "2312". It is also not unlike what Arthur C. Clarke described in his novel "Rendezvous with Rama".

What we see here is the inside of a hollowed out asteroid, pressurized and filled with a breathable atmosphere. Like I described in the previous scene, the whole structure is put into a revolving rotation, simulating the effect of gravity toward the inside "walls" of the cylinder shape we see. The structure in this scene has a diameter of about 7 kilometers and revolves with a speed of 1 rotation every 2 minutes, simulating the effect of 1g (the gravity pull we feel on Earth) at the surface of the inside. This place is also filled with water, creating lakes and seas wrapped along with the landscape. An artificial sun is running along a rail in the middle of the space, simulating a daylight cycle.

This scene is of course built from scratch, but I used countless satellite photos of the Earth to texture the landscape. I actually used a slightly warped world map to create the outlines between land and water, as some may notice a couple of familiar shorelines."\(^{[3]}\)

The astronomer and astrophysicist Carl Sagan in, Pale Blue Dot, imagined there would be human settlements on asteroids and comets within the inner-most asteroid belt (between Mars and Jupiter), the Kuiper Belt, and lastly along the comets in the Oort Cloud (roughly one light year from Earth). He imagined humans one day being able to settle on these little worlds and redirecting and maneuvering them in order to use them as "space ships" to eventually leave the solar system and set sail for the stars.

This article is licensed under a CC BY-NC-SA 4.0 license.


1. Pearson, J. (1975). "The orbital tower: a spacecraft launcher using the Earth's rotational energy" (PDF). Acta Astronautica. 2 (9–10): 785–799. doi:10.1016/0094-5765(75)90021-1.

2. Aravind, P. "The physics of the space elevator" (PDF). Am. J. Phys., Vol. 75, No. 2, February 2007

3. Wernquist, E. Terrarium - (Unnamed asteroid, main asteroid belt). Retrieved from

Further Studying

1. Sagan, Carl (1994). Pale Blue Dot: A Vision of the Human Future in Space (1st ed.). New York: Random House. ISBN 0-679-43841-6.

2. Isaac Arthur. "Upward Bound: Space Elevators". Online video clip. YouTube. YouTube, 09 March 2017. Web. 27 April 2017.

3. Isaac Arthur. "Megastructures E04: Rotating Habitats". Online video clip. YouTube. YouTube, 07 December 2015. Web. 27 April 2017.

4. Patel, Neel. “How to Turn an Asteroid Into a Spacecraft. It’s totally possible, and totally worth it.”. Inverse, Neel Patel, April 24 2017,


1.  This strategy of “covering” the spaceship (or other human living space) with rock, ice, and/or water is something that we can take advantage of on many worlds. Take for example Mercury or the Moon—worlds which have immense lava tubes (which are basically just underground, cave-like tunnels) through which lava had once flowed long ago. By constructing infrastructure and living quarters within them, all of the materials (in some cases rock, in others ice or water, and sometimes a combination of those materials) would “shield” us from dangerous micro-meteorites and cosmic rays. It’ll turn out to be valuable, later on, to accept this “shielding strategy” as a general principle which can be utilized on many worlds. We’ll discuss later on, in detail, how this shielding strategy can be used on Mercury, the Moon, and other worlds.