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Jena Johnson
Graduate Student

For me, the treasures of the deep sea are not pirate's chests of gold or mysterious shipwrecks, but the ferromanganese nodules found on the seafloor thousands of meters below the ocean's surface. These nodules are made of iron (relative concentration shown in blue) and manganese (relative concentration shown in green) oxides, and often also contain rarer elements such as copper (relative concentration shown in red - appears yellow). I am especially intrigued by both the thin, wavy laminae of this nodule and how these nodules represent the first step of manganese deposition as Mn oxides - which often have a complex sedimentary cycle after nodule burial. I study the manganese cycle as a proxy for oxygen: the oxidation of manganese is only known to occur by molecular oxygen, making manganese an excellent proxy for the rise of oxygen billions of years ago. [Sample provided by V. Orphan from a South Pacific Gyre expedition]


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