Unlike earlier mapmakers, who had to see the objects they were surveying for maps, oceanographers have been able to chart the mountains and valleys of the seabed with sonar.
Sonar sends out an acoustical pulse, which bounces off an object of the deep ocean. In 1958, the United States Office of Naval Research purchased Piccard’s bathyscaphe, which he called the Trieste. From then on, Piccard’s son, Jacques, and navy engineers worked together to uncover the secrets of the deep.
In January 1960, Piccard and an American, Donald Walsh, prepared for a dive to the deepest known spot in the world’s oceans, the Challenger Deep in the Marianas Trench in the Pacific Ocean-36,198 feet below sea level. On the day of the dive, the seas pitched and heaved, soaking the two men as they clambered aboard the Trieste. Minutes later, the sub descended into the depths. At 2,400 feet, the last rays of sunlight disappeared. At 18,000 feet, the small craft sprung a leak, but the enormous water pressure on the hull squeezed the metal shut.
At 29,000 feet, Piccard dumped iron ballast from the sub, slowing the descent. Just past 35,000 feet, the men detected the return of a sound signal, indicating that the bottom was near. At 35,800 feet, Trieste settled gently on the seabed. At that depth, the pressure was a crushing 16,000 pounds per square inch.
Walsh and Piccard peered through the windows for signs of life. There, on the muddy floor, Piccard spotted a flatfish eighteen inches long. Even here, life existed. After 20 minutes, the men set the Trieste in motion toward the surface.
At 4:56 P.M., they broke the ocean surface, having gone just 398 feet short of the deepest spot on earth.