OH-band depth and NUV absorption of hydrated carbonaceous chondritic meteorites. The meteorite sample spectra are from Hiroi et al. (2021) (available at the RELAB database). Open symbols indicate the powder samples and filled symbols indicate chip samples. CMs are classified into those with (circle) and without (triangle) the 0.7 μm band absorption. Squares with lines show the heating experiments of Ivuna (CI1) and Murchison (CM2) conducted in Hiroi et al. (1996b,a). Unheated Ivuna and Murchison are shown by squares with circles inside. CM(D), CM(U), and CI(D) are ATCCs.