As I read the spectra, we have just discovered Goethite on Mars!
Why is this not even mentioned on the NASA website?
And from Mars:
Please pay attention to the peak around 750 nm and the dip around 900 nm.
Now what is Geothite?
GOETHITE FeO(OH) Orthorhombic
Description: Goethite is a common iron mineral. It often forms by weathering of other iron-rich minerals, thus is a common component of soils. It may form excellent pseudomorphs after the original minerals particularly pyrite or marcasite. Goethite may also be precipitated by groundwater or in other sedimentary conditions, or form as a primary mineral in hydrothermal deposits.