The deepest known point on Earth is at the bottom of the Mariana Trench, a depression in the floor of the western Pacific Ocean, just east of the Mariana Islands. This trench is 1,554 miles long and 44 miles wide. Near its southwestern extremity (210 miles southwest of Guam) lies the deepest point on Earth. This point - known as the Challenger Deep - is where the ocean bottom lies at a depth of nearly 7 miles (variously reported to be at least 36,198 to 38,518 feet deep). In 1960, the Trieste, a manned submersible owned by the U.S. Navy, descended to the bottom of the Mariana Trench. The depth reported is still only an estimate, based on a mathematical conversion from measured pressure (more than 8 tons per square inch), interpreted in terms of the integral of water density from the surface to the bottom.