This figure shows a Mture in the spectrum is the doublet colored in
yellow that results from a jarosite phase. This phase contains water,
in the form of hydroxyl, as a part of its structure. This is
mineralogical evidence for water-driven processes on Mars.  Besides
the jarosite phase (yellow) also a magnetic phase (blue), attributed
to an iron oxid, has been identified in this rock, as well as a Fe-2+
silicate phase (green) and another Fe-3+ phase (red).