Polymetallic Nodules and Deep-Sea Mining: The Ocean's Hidden Battery Metals and the Glomar Explorer Tale

About this episode

This Rest Is Science episode uses a mix of geology, history and physics to explore polymetallic nodules on the ocean floor, how they form, what metals they contain, and why they matter for battery metals. It also revisits the Glomar Explorer revelation tied to a Cold War CIA operation and the question of ocean mining as a source of battery metals. Along the way, the hosts answer audience questions on ambidexterity, handedness and how lightning affects large animals.

Key insights

• Polymetallic nodules are rock-like deposits rich in manganese, nickel, cobalt and more.
• Hydrogenous precipitation forms nodules, a process that occurs extremely slowly over millions of years.
• Deep-sea mining presents a potential path to secure supply chains for batteries but environmental trade-offs must be weighed.
• Cold War theatre and science can intersect in unexpected ways, as shown by the Hughes managed operation.

Overview

The Rest Is Science examines the science and history around polymetallic nodules found on the ocean floor, their slow formation, and their potential role in supplying metals critical for batteries. The episode also recaps a Cold War era episode involving Howard Hughes and the Glomar Explorer, illustrating how scientific narratives can intersect with geopolitics and showmanship. In addition to the main topic, the hosts engage with rapid-fire questions on ambidexterity, left-handedness and neuropsychology, and even touch on lightning physics and animal safety during storms.

What are polymetallic nodules

Polymetallic nodules are rock-like concretions scattered across the ocean floor. They accumulate metals such as manganese, nickel, cobalt and copper through a hydrogenous process that precipitates dissolved metals from seawater onto an existing seed core. The formation is incredibly slow, with growth around about 1 millimeter per million years, which means most nodules are the size of a potato or grapefruit and can contain valuable metallic cores with complex, layered structures.

Formation and structure

The nodules begin when a small seed particle—possibly a shark tooth, a megafauna fossil, or a meteorite fragment—settles on the seabed. Over immense timescales, minerals in seawater, including manganese, nickel, cobalt and copper, are absorbed and precipitated onto the seed, creating concentric, layered shells. This process makes nodules natural batteries that can sustain electrical charge when many nodules cluster together. Their geology is intimately tied to the long history of oceanic volcanism and hydrothermal activity, which supply the metals that accumulate in the nodules.

Implications for energy and mining