Ferrihydrite:
A recent study revealed that the red color of Mars could be due to the presence of an iron-containing mineral called ferrihydrite.
- It is a poorly crystalline nanomineral built up of about 20% (FeO4) and 80% (FeO6) polyhedra.
- It forms by rapid oxidation and hydrolysis, and exists in varying degrees of structure disorder.
- It is one of the initial corrosion products in the oxidation of iron, and is the precursor to the formation of the more stable mineral phases goethite (α-FeO(OH)) and hematite (α-Fe2O3 ).
- It is widespread in the soluble fraction of soils and weathered rock.
- In precipitates around cold and hot springs, especially those supporting iron-metabolizing bacteria; in acid mine effluent.
- The iron bacteria, especially Gallionella ferruginea, Leptothrix ochracea and Toxothrix trichogenes create ferrihydrite as a waste product of their metabolism.
- It is known to trap water and protect organic molecules and forms rapidly in cool water.
