FERRIC IRON IN PRIMITIVE ASTEROIDS - A 0.43-MU-M ABSORPTION FEATURE

A 0.43-μm absorption feature has been identified in 12 high-resolution UV/visible spectra of asteroids. Eleven of these asteroids are of the primitive C, P, G classes. The 12th asteroid is an S-class asteroid that does not show the 1.0-μm mafic silicate absorption feature. Spectra of six additional primitive asteroids, including two D-class asteroids, do not show the absorption feature. The feature is attributed to a ferric iron spin-forbidden absorption present in minerals created as a result of aqueous alteration, and is often seen in conjunction with absorption features attributed to phyllosilicates as a result of aqueous alteration activity. A search for the 0.4-μm Soret band indicative of organic porphyrin compounds was unsuccessful. © 1993 by Academic Press, Inc.