Set sail December 21, 1872,
Portsmouth, England
Docked May 24, 1876,
England
The idea for the H.M.S. Challenger expedition, which investigated the physical and biological properties of the world’s oceans, began with two British naturalists, William B. Carpenter and Charles Wyville Thomson. Having already dredged in the North Atlantic Ocean off the coast of Britain, they realized a wealth of information could be obtained from the oceans if they were examined in a systematic way.
Prompted by Carpenter, the Royal Society, the major scientific society in Great Britain, asked the British Admiralty to supply a ship and crew to make such a voyage. The request was granted. Naval command was given to Sir George Nares, while Thomson was put in charge of scientific research. The instructions given to these men were to:
investigate the physical condition of the deep sea throughout the three great ocean basins, that is, to ascertain their depth, temperature, circulation, etc. to determine the distribution of organic life throughout the areas traversed, at the surface, at intermediate depths, and especially at the deep ocean bottom.
Nares and Thomson were provided a 226-foot-long combination steam and sailing vessel, which they named the Challenger. The party set sail from the British naval harbor at Portsmouth on December 21, 1872. During the course of the expedition, the ship stopped every 200 miles and stayed in place to record ocean depths, to dredge for animal life, and to take the temperature of the ocean at different depths. It performed these operations at 362 stations, dredging as deep as 5,486 meters (18,000 feet).
The Challenger expedition was the first to systematically record the differences between the Atlantic and Pacific oceans. The Pacific, for example, is considerably deeper and has a clay bottom. Challenger scientists found the first deposits of manganese, a potentially valuable mineral, in the mid-Atlantic on March 7, 1873, at a depth of 1,500 fathoms (9,000 feet); they later found manganese on the floor of the Pacific as well.
Traveling every ocean except the Arctic and crossing the equator six times, the voyage covered 69,000 nautical miles (79,000 statute miles). The expedition took a two-month break in Australia in March and April 1874 so the scientists could spend their time ashore studying freshwater biology. While cruising in the Pacific in 1875, the ship encountered ocean depths so much greater than had been thought possible that their thermometers, used to measure the ocean temperature at various depths, broke under the unexpected pressure. The varying measurements of the ocean floor convinced the geologists of a revolutionary idea—there were mountain ranges under the sea.
The Challenger returned to England on May 24, 1876, carrying “a great freight of facts.” Besides adding 715 new genera and 4,717 new species to man’s knowledge of marine zoology, Challenger scientists found life at depths much greater than ever before suspected. They also revealed the physical and chemical nature of the ocean floor, obtained seawater for chemical analysis, and gained new information about the circulation of the ocean currents. They mapped the contours of ocean basins, including the Atlantic Ridge and the Challenger Deep, located in the western Pacific Ocean in the Mariana Trench. The report of the Challenger expedition took 23 years to compile and filled 50 volumes.
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