Explanation:

 What are Polymetallic Nodules?
Polymetallic nodules (PMN) are also known as manganese nodules.
They are potato-shaped, largely porous nodules found in abundance carpeting the sea floor in the deep sea of the world oceans.
Besides manganese and iron, they contain nickel, copper, cobalt, lead, molybdenum, cadmium, vanadium, titanium.
Of these metals nickel, cobalt and copper are considered to be of economic and strategic importance

The permission for exploration of Poly-Metallic Nodules (Manganese Nodules or PMN) in the Central Indian Ocean Basin region was granted in 1987, and India was the first country to have received such permission under the UN Law of the Sea. “Deep Ocean Mission” is an extension of India’s programme of PMN exploration.
? The Government of India through the Ministry of Earth Sciences recently signed a contract with the International Seabed Authority for exploration of Poly-Metallic Sulphides (PMS). The contract permits India to explore PMS along the Central Indian Ridge and the Southwest Indian Ridge of the Indian Ocean.