The percentage of the ocean floor now accessible by Alvin, the iconic US research submersible. The little boat was commissioned in 1964, and is best known for carrying the first explorers to the wreck of the Titanic in 1986. Its original service depth of 4,500 meters — about three miles — meant it could reach 68% of the ocean floor, but a recent upgrade, including a new titanium hull and stronger seals, now allows it to reach 6,500 meters or four miles down. It will allow scientists to study places such as the Aleutian Trench in the northern Pacific, believed to teem with living things: “People know they’re there,” one researcher told Science, “but nobody’s had a good look.” An initial mission is now under way. |