1999A&AS..135...65F

In the last year we have started a spectroscopic investigation of asteroids located in the region of the main-belt between about 2.2 and 3.6AU. The aim of this work is to study the aqueous alteration process which acted in that zone, dominated by low albedo C-type asteroids, and to compare the spectra of these hydrous objects with those of CM2 carbonaceous chondrite meteorites. In fact, the spectra of these meteorites reveal features probably due to aqueous altered materials on their surfaces. The study of the aqueous alteration process can give important information on the chemical and thermal evolution of the earliest Solar System. More that 65% of the investigated objects have revealed features suggesting the presence of hydrous materials. The comparison of the spectra of the hydrated asteroids obtained to date with those of several CM2 carbonaceous chondrite meteorites seems to indicate that aqueous altered asteroids could be the parents of CM2 meteorites. The data have been obtained during several observational runs at the Asiago Observatory with the 1.8m telescope and at ESO-LaSilla with the 1.5m telescope.