Brightness variations of comet surface - CIVA
Zooming in to a portion of the fractured cliff face imaged by Philae's CIVA camera 4 reveals brightness variations in the comet's surface properties down to centimetre and millimetre scales. The dominant constituents are very dark conglomerates, likely made of organics. The brighter spots could represent mineral grains, perhaps even pointing to ice-rich materials.
More images of comet 67P/Churyumov-Gerasimenko can be found in the '67P - by Rosetta' collection.