3-Micron Spectrophotometric Survey of M and E-class Asteroids
Icarus, vol. 117, pp 90-100.
Many asteroids show absorption features diagnostic of hydrated
minerals in the 3-micron region
of the spectrum. Reflectance studies in this region can determine the
hydration state of
surface minerals, and by inference, the thermal histories of bodies. We have made
spectrophotometric observations of eight E-class, M-class, X-class and P-class asteroids in December 1991 and eight E-class and M-class asteroids
in August 1993
using the Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. In 1991 we discovered a 3-micron absorption band on the E-class asteroid 44 Nysa and the P-class asteroid 50 Virginia, and found a possible absorption on the E-class asteroid 64 Angelina. We confirmed the presence of a
3-micron absorption band on 44 Nysa and on the M-class asteroid 92 Undina (Jones et al. 1990) and detected this feature on
the M-class asteroid 201 Penelope in 1993. These data demonstrate that high-albedo and medium-albedo
objects such as E- and M-class asteroids can be hydrated and need not be interpreted as primarily of igneous origin. We revise the interpreted mineralogy of some E and M-class asteroids as a result.