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　　科技类文章阅读：                                                                                          The Relaunch of an Ocean Workhorse

　　摘自American scientist.

　　On its 50th birthday, the Alvin submersible follows up on its legacy of discovery with some upgrades that will let it become even more useful in ocean exploration.

　　Heather Olins

　　August 15, 2014

　　I wake early—too excited to sleep much the night before—and eat a quick breakfast, avoiding liquids in the hopesof not having to use the (non-existent) facilities in the sub. I stand by anxiously while the sub crew preps Alvin with intimidating precision, focus, and expertise. I watch as Alvin is ceremoniously and slowly wheeled out along its deck tracks—caretakers in tow performing final checks and preparations. I remove my shoes, climb the stairs, and descend into "the ball," as the inside compartment of Alvin is nicknamed because of its spherical shape.

　　I wait eagerly as the sub is lifted by a large crane, dangled over the stern of its mother ship the R/V Atlantis, and slowly lowered into the water. We float at the surface, bobbing with the waves, the view alternating between clouds and inches below the surface. Eventually the “all clear” signal is given and we begin to descend. The sensation of movement ends as soon as we're below the surface. The external world gradually darkens. Black becomes blacker than I thought possible. But, the black is punctuated with blue flashes—a bioluminescent light show by a company of plankton, fishes, and organisms that look like goo, put on for our entertainment throughout this journey into the deep.

　　A Half-Century in the Deep

　　Fifty years ago, on August 4, 1964, the Alvin submersible made its first free dive. At the time, most marine scientists didn’t see much value in sending a person to the ocean’s depths for research. For the better part of the previous century, oceanography and marine biology had been carried out from the decks of ships—sending sampling devices down into darkness and hoping for the best upon their return. Old habits die hard.

　　Owned by the US Navy and operated by Woods Hole Oceanographic Institute (WHOI) in coastal Massachusetts, Alvin wasn’t the first deep submergence vehicle (DSV) to carry scientists into the deep. But it was the first to prove its value to the scientific community, and it has changed how we think about and study our oceans. By enabling geologists to see seafloor rocks within the context of the environment, and allowing biologists to decide precisely where to sample, it has become indispensable for deep-sea research.

　　Alvin is about the size of the front half of a school bus, but weighs twice as much, and carries only three people. It is small compared to Navy submarines but dives far deeper; in comparison Navy subs barely scratch the surface. You may think of submarines as torpedo shaped, but Alvin has been said to resemble a giant toilet. It is white with a bright red “sail” on top. Bobbing at the surface it tends to look a bit out of place, but it shines in its intended environment.

　　It is not the newest or deepest diving DSV, but it has the longest legacy, the most experience, and is the best known. Alvin has been involved with many of the most important marine discoveries of the past half-century. Its accomplishments include finding a lost hydrogen bomb for the US Air Force, helping geologists determine how new ocean crust is formed, and discovering deep-sea hydrothermal vents and their associated ecosystem based on chemical energy from inside the Earth (prior to this discovery, it was thought all life depended on the Sun for energy).

　　It has been used by archaeologists to explore the wreck of the RMS Titanic, and it has been instrumental in the discovery of countless new species, many types of which are difficult or impossible to collect from a ship’s deck. More recently, Alvin has helped describe the impacts of the Deep Water Horizon oil spill. Alvin has completed more than 4,700 dives, has been referenced thousands of times in the scientific literature, and has become an indispensable tool for probing the mysteries of the deep.

　　And there is plenty left for Alvin to do. We have better maps of Mars and the Moon than we do of our own sea floor. Ninety-five percent of the marine world has never been seen or imaged. The ocean covers 71 percent of Earth’s surface and contains 97 percent of its water. Eighty percent of space available to living things on this planet is in the ocean below 1,000 meters (about 3,000 feet). The ocean regulates aspects of world climate, is an important food source, and holds unexplored reserves of biodiversity and mineral resources. Research vessels such as Alvin help us learn about this mysterious world.

　　A New Alvin for the Next 50 Years

　　Alvin didn’t touch the water from 2011 to 2013 because it was being upgraded. Throughout its “life” it has undergone periodic maintenance and renovations every few years. By its 30th birthday, engineers confirmed that there was no single part remaining from the original sub. It maintains the same name, and a continuous record of dive numbers creates a single identity.

　　The most recent upgrade was perhaps the most substantial. The titanium sphere that holds the pilot and two observers has been replaced with one that has two additional windows (bringing the total to five) and is six inches wider. This increase might not seem like much, but it grows the interior space by about 18 percent. That added comfort is welcome when you are confined to the sphere for eight hours. The two new viewports allow the scientists and pilot to simultaneously look at the same location in front of the sub. Previously, the passengers and pilot could not look at the same spot together, making sample collection tricky.

　　The upgraded sub now boasts touch screen controls and new navigation systems, enabling the pilots to focus more on sample collection. New lighting and imaging systems will take better images and video than ever before. Phase two of the upgrade involves a new battery, system but once completed, Alvin will be able to dive to 4 miles (6,500 meters), so it will be able to access 98 percent of the seafloor. The current limit is 2.8 miles (4,500 meters), where it can reach 63 percent of the seafloor. This additional depth would be like studying the United States without access to the western part of the country or Texas, and then all of a sudden being able to explore all but New England. With these new capabilities, Alvin’s future is bright… well, actually dark—that’s the whole point.

　　The following slideshow gives before and after images that show upgrades to the Alvin sub. The new Alvin went on its first test cruise earlier in 2014.

　　Visiting the Seafloor

　　After about two hours we reach the seafloor, a mile and a half deep, and begin our work. I’m lucky to have a particularly exciting dive. We get to explore massive rock chimneys billowing what looks like black smoke and covered with exotic animals. Other dives might search for rocks from new lava flows, test a new instrument, or collect an experiment deployed a year ago.

　　In what feels like minutes, but really is more like four hours, the pilot informs me time is almost up. I pick the most important item left on my to do list—collecting one more chunk of rock from a hydrothermal vent chimney. When the allotted power is used up and the pilot refuses my “just one more sample” request, we begin the ascent. All went well, and so as I rewatch the blue light show, my caffeinelike anticipation from the descent has been replaced with a relaxed satisfaction and the knowledge that I have experienced something truly amazing that few others ever will.

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