The components of the surface of Mercury

Caption NASA originale:"Updated calibration and subsequent mosaicing have led to substantial improvements in the Mariner 10 color image data. This color composite was formed to especially highlight differences in opaque minerals (such as Ilmenite), Iron content and soil maturity.
K - Crater Kuiper shows color consistent with fresh material excavated from a subsurface unit that may have an "unusual" composition;
D - relatively dark and blue unit consistent with enhanced Titanium content;
B - bright red unit that may represent primitive crustal material
F - color unit that follows plains boundaries, interpreted as lava flows".