What is the composition of carbonaceous type asteroids?

Question

Please be specific about the kind of materials found on ceres and which of these can be used for the construction of a pace settlement.

Answer 1

C-type (carbonaceous) includes more than 75 percent of known asteroids. Very dark with an albedo of 0.03-0.09. Composition is thought to be similar to the Sun, depleted in hydrogen, helium, and other volatiles.

Carbonaceous asteroids are typically very dark in color, darker than coal in fact. This is because they are extremely rich in carbon compounds and other dark materials, common in the outer middle regions of solar systems.

Among the most common types of asteroids, these are also the bodies which tend to pose the greatest risk to planets. However, they do have their uses as habitat construction material, and represent a rich source of income for asteroid miners dealing with space development firms.

Rich in carbon, these bodies are largely pristine and unchanged objects, relics from the formation of their solar system. Rich in organic compounds, they are fairly reddish in coloration, and may contain sizable reservoirs of volatiles such as water ice.

Ceres:

The outermost layer is likely made of icy material including water and ammonia. The fact that Ceres has not lost these volatile components in destructive impact events means that its composition probably preserves a record of what the solar system was like when it was first condensing from dust into planetesimals and larger protoplanets. Ceres may well be a relict protoplanet.

New observations of Ceres in the 2–4 μm spectral region were obtained in May 2005 using SpeX on the IRTF. Analysis of thermally-corrected spectra indicates the presence of carbonates at an abundance of 4–6% on Ceres’ surface, similar to what is seen in CI meteorites. These carbonates are responsible for bands in the 3.3 and 3.8–3.9 μm region. Iron-rich phyllosilicates or ammonium bearing phyllosilicates can both account for an absorption band at 3.05 μm, but consideration of mid-IR data from Cohen et al. (1998) leads us to favor iron-rich phyllosilicates. Such minerals, including cronstedtite, are commonly found in carbonaceous chondrites and suggest relatively oxidized precursors and aqueous alteration that did not go to completion.

We use the clathrate hydrate trapping theory and gas drag formalism to calculate the composition of ices incorporated in the interior of Ceres. Utilizing a time-dependent solar nebula model, we show that icy solids can drift from beyond 5 au to the present location of the asteroid and be preserved from vaporization. We argue that volatiles were trapped in the outer solar nebula in the form of clathrate hydrates, hydrates and pure condensates prior to having been incorporated in icy solids and subsequently in Ceres. Under the assumption that most of volatiles were not vaporized during the accretion phase and the thermal evolution of Ceres, we determine the per mass abundances with respect to H2O of CO2, CO, CH4, N2, NH3, Ar, Xe and Kr in the interior of the asteroid. The Dawn space mission, scheduled to explore Ceres in August 2014, may have the capacity to test some predictions. We also show that an in situ measurement of the D/H ratio in H2O in Ceres could constrain the distance range in the solar nebula where its icy planetesimals were produced.

Answer 2

Here's an article on Ceres. It looks like it's mostly amonia and water on the surface and not carbon.

Here's more on carbonaceous meteors and asteroids. They have traces of organic stuff in them.

http://en.wikipedia.org/wiki/Carbonaceous_chondrite