• Scattered across an abyssal plain known as the Clarion-Clipperton Zone (CCZ) are polymetallic nodules that are a potato-sized prize for mining companies in search of materials needed for humanity's green energy transition.

• A new study analyzing these modules reveals that these rocky lumps are capable of producing "dark oxygen" 4,000 meters below sea level where light cannot reach.

• While this discovery could upend our understanding of how life started on Earth, the study also complicates negotiations around deep-sea mining regulations as it showcases how little we really know about the ocean's depths.

Nestled between Hawaii and the western coast of Mexico lies the Pacific Ocean's Clarion-Clipperton Zone (CCZ), a 4.5 million-kilometer-square area of abyssal plain bordered by the Clarion and Clipperton Fracture Zones. Although this stretch of sea is a vibrant ecosystem filled with marine life, the CCZ is known best for its immense collection of potato-sized rocks known as polymetallic nodules. These rocks, of which there are potentially trillions, are filled with rich deposits of nickel, manganese, copper, zinc, cobalt. Those particular metals are vital for the batteries needed to power a green energy future, leading some mining companies to refer to nodules as a "battery in a rock."