Ceres has one-tenth of the total water in Earth’s oceans. The solar irradiance of 150 W/m2 at aphelion, one ninth that on Earth, is high enough for solar-power facilities. The total volume of water on Earth is about 1.4 billion cubic kilometers, around 41 million of which is fresh water. If Ceres’ mantle accounts for 25 percent of the asteroid’s mass, that would translate to an upper limit of 200 million cubic kilometers of fresh water (5 times more fresh water than Earth).
Ceres has about one third of the mass of the whole asteroid belt and is the sixth-largest body in the inner Solar System by mass and volume. The inner solar system includes the asteroid belt and every thing closer to the sun than the asteroid belt. Ceres has a round shape, and a surface gravitational acceleration about 2.8% that of Earth. It has a surface area approximately 1.9% of Earth’s dry land, slightly larger than the total land area of Argentina.
It is more energy-efficient to transport resources from the Moon or Mars to Ceres, than from Earth. Transportation from Mars or the Moon to Ceres would be even more energy-efficient than transportation from Earth to the Moon.
Ceres has a very low escape velocity (0.51 km/s) and the great amount of water on Ceres would not only be a resource for a colony’s own use, but would also be an exportable resource, supplying fuel, oxygen, and water for ships going through and beyond the main belt. This water, together with metal structures built in zero gravity from asteroidal materials, would allow colonists to trade for raw materials and refined products that are needed but not available in the main belt.
Settlement of Ceres
Growth of the settlement will be facilitated through the use of locally or regionally available materials. On Ceres, the surface might be covered with regolith, solid rock/ice, or a mixture. A solid surface could allow for excavated structures, as well as built structures using excavated materials. A regolith surface could be used in “sandbag” type structures, or, perhaps, provide raw material (i.e., carbon) for processed forms (i.e., carbon-fiber rods and sheets). Regionally available material includes, most importantly, iron and other metals from elsewhere in the main belt. A metallic asteroid 10 meter in diameter contains over 500 m^3 of material, enough to build a 5 meter diameter tube, with walls 2 cm thick, over 1500 meters in length.
Zubrin envisions trade between the Asteroid Belt, Mars and Earth
While settlers could initial deal with Ceres’ low gravity (less than 3% of Earth’s) by means of exercise and other strategies that have been employed by astronauts in Earth orbit, in the long term, new approaches are needed. The use of “doughnut trains” is one approach. Surface or subsurface habitats could be constructed to run on a circular track that is angled inward, so that as the habitat moves around, the occupants experience the reactive centrifugal force as if they were in a higher-gravity environment, which could be set to approximate the gravity of Mars, the Earth, etc. The habitat would be built to cover the whole track, and so form a continuous loop. It is similar to various proposals for orbital colonies, but does not need to include all of the living space: settlers might spend only half of their time in the train, with the rest being in low-g work environments elsewhere about the surface, such as in greenhouses, shops, and mines.
SOURCES – Wikipedia, Use of Ceres in the Development of the Solar System by Zachary V. Whitten, The Economic Viability of Mars Colonization by Robert Zubrin