(21) Lutetia spectrophotometry from Rosetta-OSIRIS images and comparison to ground-based observations

Here we present some preliminary results on surface variegation found on (21) Lutetia from ROSETTA-OSIRIS images acquired on 2010-07-10. The spectrophotometry obtained by means of the two cameras NAC and WAC (Narrow and Wide Angle Cameras) is consistent with ground based observations, and does not show surface diversity above the data error bars. The blue and UV images (shortward 500 nm) may, however, indicate a variegation of the optical properties of the asteroid surface on the Baetica region (Sierks et al., 2011). We also speculate on the contribution due to different illumination and to different ground properties (composition or, more probably, grain size diversity). In particular a correlation with geologic units independently defined by Massironi et al. (2012) is evident, suggesting that the variegation of the ground optical properties is likely to be real.

► Preliminary analysis of surface variegation on Lutetia from OSIRIS images.
► NAC and WAC spectrophotometry is consistent with ground based observations.
► Indications of optical properties variegation in Blue and UV images.
► Illumination and composition contribution separated only at a zero level.
► Correlation between geological units and variegated regions found.