Mathilde and Eros: C-Type and S-Type

Caption NASA originale:"In this montage, Mathilde (at left) and Eros (at right) are shown at the same scale, as they were imaged by NEAR Shoemaker from about 1.800 Km on June 27, 1997, and February 12, 2000, respectively. Mathilde is 56 Km across and Eros is 33 Km long and 13 Km wide. However, Mathilde's brightness is greatly exaggerated for viewing purposes - it's actually 6 times darker than Eros, with about the same reflectivity as soot! In a scheme that reflects how asteroids have historically been a topic for astronomy, not geology, they are classified into groups based on their colors as observed through telescopes. The 2 major classes of asteroids are called S-Types and C-Types. S-Types, whose colors are consistent with "stony" or rocky compositions, prevail among asteroids that orbit closer to the Sun than the mid-point of the asteroid belt. Eros and the 2 asteroids encountered briefly by the Galileo spacecraft on its way to Jupiter - Gaspra and Ida - are all S-Types. C-Types like Mathilde have a dark gray color consistent with a "carbonaceous" composition, rich in carbon compounds and other dark materials. They prevail in the outer part of the asteroid belt".