How did the Challenger Expedition begin systematic scientific study of the oceans?

The Challenger Expedition (1872–1876) is widely recognized as the first major, systematic undersea survey, establishing the foundations of modern oceanography.12

The expedition began following successful preliminary voyages by the British ships Lightning and Porcupine in 1868 and 1869, which revealed significant oceanographic data. Authorized by the British Admiralty in cooperation with the Royal Society, the Challenger was specifically tasked with determining the conditions of the deep sea across the world's great ocean basins.31

Under the scientific supervision of Sir C. Wyville Thomson, the crew occupied 362 stations, conducting extensive deep soundings, dredgings, and biological investigations. By systematically measuring the physical and chemical properties of seawater—such as temperature, salinity, and current patterns—and mapping the topography of the seafloor, the expedition provided a comprehensive dataset that remains a landmark in undersea exploration. The resulting findings, published in 50 volumes, transformed the ocean from a mysterious expanse into a subject of rigorous, multidisciplinary scientific inquiry.132