A small-body paper made a Nature group journal, Nature Astronomy:
Beck, P. Quirico, E. Poch, O. et al. On the darkness of Ryugu and other dark small bodies s41550-025-02557-z
The carbonaceous asteroids (those in the C-complex) resemble the carbonaceous-chondrite meteorites. These are dark (even for a meteorite) and organic-bearing. Now that we have samples from Ryugu and Bennu, we can confirm that, yes, C-type asteroids are organic-bearing. This was widely thought to be why C-complex asteroids (and comets) have low, flat albedos (low reflectivity). However, the exceptional blackness of some asteroids like Ryugu (~4 percent of light reflected) led some to suspect exceptional organic content. Beck et al. have published a ‘not so fast there’ paper. In addition to organics, numerous other components can act as blackeners (light absorbers). In particular, they single out fine iron grains as darkening agents.