Definition
A D-type asteroid is a category of asteroids characterized by very low reflectivity and a reddish-brown to dark-brown color. Their spectrum suggests the presence of complex organic materials, hydrocarbons, and volatile substances. These bodies are considered witnesses of the primitive matter of the outer solar system.
Composition
The surface contains carbon macromolecules, altered silicates, and traces of ices. The low brightness and color indicate an abundance of dark organic substances, similar to those found in some carbonaceous meteorites.
Internal structure
The internal structure is thought to remain largely undifferentiated, consisting of a mixture of ice, silicates, and organic compounds. High porosity and low density suggest weak internal cohesion and formation through the agglomeration of fragments.
Distribution and origin
D-type asteroids are mainly found in the outer regions of the asteroid belt and beyond, including the trojans and trans-Neptunian populations. Their origin is linked to the cold regions of the early solar system where ices and organic materials accumulated.
Evolution
Over time, solar radiation and impacts have modified their surface, but the internal composition remains close to that of the original materials. They represent a reservoir of information about the earliest stages of the chemical and physical evolution of the solar system.