Spectral Types

On approach to Adalia the pioneers executed a system-wide scan of all major and minor bodies, including the 250,000 asteroids exceeding a radius of 1km. Spectral types were assigned based on their emission spectrum, color, and surface albedo. The four most prominent groupings were assigned types C, S, M, I with the remaining asteroids composed of portions of them.

Distribution
The spectral types are distributed throughout the main belt in varying compositions. The results of the survey have been plotted:



C-type
C-type (carbonaceous) asteroids are the most common spectral type, with 65% being pure C-type. Composed of carbon compounds, water, and minerals like Serpentine and Olivine, they are found throughout the belt, inner, main and outer, but have the highest concentration in the main belt, around 2 AU semi-major axis. C-type is also found in Cm, Ci, Cs, Cms, and Csi mixed-type asteroids.

S-type
S-type (stony) asteroids are the second most common spectral type, with under 10% being pure S-type. They are composed of iron and magnesium silicates like Pyroxene, Olivine, and Chromite and contain little to no water. They are found predominantly in the inner and main belts with the highest concentration around 1.6 AU semi-major axis. S-type is also found in Cs, Cms, Csi, Sm, and Si mixed-type asteroids.

M-type
M-type (metallic) asteroids are fairly uncommon, with less than 5% being pure M-type. They are bright asteroids that are the remaining pieces of the metallic core of early minor planets and made up primarily of nickel-iron. They are found in the main belt with the highest concentration around 1.8 AU. M-type composition is also found in Cm, Cms, and Sm mixed-type asteroids.

I-type
I-type (icy) asteroids are the rarest and least accessible with only 1.25% in the main belt being pure I-types. They are very dark and composed of rock and frozen volatiles like methane, ammonia, and water. They are found solely in extreme outer belt around 3 AU, and orbit in the L4 and L5 Lagrange points of the massive Adalia C planet.