Introduction to Exploring the Ocean Abyss

The deep ocean is a world that seems as alien to human beings as a planet in a science-fiction novel. It is a realm of absolute darkness, where sunlight never penetrates and the frigidly cold water exerts pressures measured in tons per square inch. The ocean floor is a landscape of rolling plains, deep canyons, and dramatic mountain chains, all formed by vigorous geologic activity. Here, molten rock from deep within the Earth forms new areas of sea floor and hot springs called hydrothermal vents belch clouds of superhot water and minerals from deep within the crust into the surrounding water. The vents and the areas around them are home to a wealth of strange creatures—microbes that feed on sulfur compounds erupting from the springs; six-foot, red-tipped worms fed by colonies of bacteria living within their guts; and bizarre animals that resemble limp dandelions.

In August 1996, scientists reported that the vents harbor a form of life that is truly alien to our world of air and sunlight. Researchers at The Institute for Genomic Research (TIGR) in Rockville, Maryland, announced that they had mapped the entire genome (genetic code) of a single-celled organism called Methanococcus jannaschii. Taken from the sides of a vent 2 miles (3 kilometers) beneath the Pacific Ocean in 1982, the organism resembled true bacteria in that it was composed of a single cell that had no nucleus. Genetically, however, it was in many ways closer to plants and animals--organisms whose cells have nuclei. Furthermore, it lived under conditions that no bacterium could survive. The TIGR scientists concluded that M. jannaschii belongs to a third kingdom of organisms—literally, a new kind of life form—the Archaea. The significance of this discovery was not completely understood in 1997, but it was already causing a revolution in biological thinking. As one researcher remarked: "It shows how little we know about life on this planet."

It is remarkable, but not surprising, that we could have shared the planet with a third branch of life for so long while knowing nothing of its existence. Even as scientists study the features of Mars and Venus, the deepest recesses of our own ocean remain largely a mystery. The ocean covers more than 70 percent of the Earth's surface—more than twice as much as all the land masses combined—and yet human beings have explored only a tiny fraction of it. But that is changing. The pace of undersea exploration is increasing, and the benefits of studying the ocean are moving beyond the realm of theory. By the mid-1990's, many geological features of the ocean floor had been mapped and many of the unusual creatures that inhabit its depths classified. Meanwhile, oceanographers were developing new tools and methods for exploring the deep, including a variety of advanced submersible vehicles. We are embarked on a real-life voyage to the bottom of the sea that promises to change the way we view the ocean.

The Geology and Life Forms of the Abyss

The ocean floor was long thought to be a barren, featureless “desert.” It seemed unlikely that the cold, black depths could be hiding anything of interest or sustaining any form of life. People referred to the deep ocean as the abyss, from the Greek word abyssos, which means “without bottom.” But as scientists began to explore ever farther beneath the ocean surface in the 1900's, it became clear that the abyss holds many interesting secrets and that its geology is strikingly varied.

If all the water could be removed from the world ocean, the continents would look like high plateaus rising above the sea floor, each bordered by a relatively shallow, gently sloping plain called a continental shelf. The continental shelves are hundreds of miles wide in some places, and nearly nonexistent in others. At a depth of about 90 to 180 meters (300 to 600 feet), the continental shelves drop off steeply to the abyss. The average depth of the ocean beyond the continental shelves is about 4,800 meters (16,000 feet), but this figure is somewhat deceptive because the ocean floor includes many tall submerged mountains as well as trenches that can be 5 to 11 kilometers (3 to 7 miles) deep.

The Abyssal Plains

About 10 percent of the ocean floor consists of abyssal plains, which marine geologists believe are the flattest areas on Earth. The abyssal plains are found in several regions, where solid particles from rivers and from the shells of tiny marine organisms settle to the bottom to form thick, smooth layers of sediments. Farther out in the ocean, most sediment comes from the shells of tiny marine organisms. The shells drift slowly down through the water when the organisms die and accumulate on the bottom. The lower layers of the sea-floor sediments become packed hard by the weight of the sediment above them. The deepest sediments are several kilometers thick and nearly 200 million years old.

Abyssal hill regions, which cover an estimated one-fourth to one-third of the deep-sea floor, are almost as flat as the true abyssal plains, but they are underlain by mountains, ridges, and valleys. These features are buried under a heavy blanket of sediment. Here and there, the top of a particularly lofty peak protrudes from the sediment.

The most prominent feature of the deep-ocean floor is the Mid-Ocean Ridge, an enormous undersea mountain chain. When explorers first discovered evidence of the Mid-Ocean Ridge in the mid-1800's, they thought there were many separate ridges in each ocean, so they gave each part of the ridge they found a different name, such as the Mid-Atlantic Ridge, which divides the Atlantic Ocean nearly down the middle. Since then, they have learned that the Mid-Ocean Ridge is a single formation stretching about 60,000 kilometers (37,000 miles) around the globe. However, the original names for its various segments are still often used.

The Mid-Ocean Ridge

The Mid-Ocean Ridge marks a line along which major plates of the Earth's crust are pulling apart at a rate of 1 to 2 centimeters (0.4 to 0.8 inch) a year to form new ocean floor. As the plates separate, molten lava rises up from below to fill the rifts (gaps), solidifying as it meets the icy-cold seawater. As the oceanic plates move away from the rifts, the valleys between the ridges slowly become filled with sediment until, after millions of years, they become abyssal hill regions.

Where an oceanic plate collides with a continental plate, a subduction zone is formed. At a subduction zone, the dense oceanic plate is forced downward, beneath the lighter continental plate, and begins a slow descent back into the Earth's interior, where it is melted down again. The colliding plates and heat make subduction zones regions of volcanic activity and earthquakes.

Subduction zones are marked by deep trenches hundreds of kilometers in length. A trench is formed when an oceanic plate drags some of the crust downward with it as it dives beneath a continental plate. Most of the world's oceanic trenches are found in the Pacific; the only major one in the Atlantic is the Puerto Rico Trench. This is the deepest point in the Atlantic Ocean: 8,648 meters (28,374 feet) below sea level. The deepest known spot on Earth is the Challenger Deep of the Mariana Trench in the central Pacific Ocean, measured at 11,033 meters (36,198 feet) below sea level.

Enormous Water Pressure

The water pressures at such depths are incredible. At the bottom of the Mariana Trench, the 11 kilometers (7 miles) of overlying water exert a pressure of more than 1,100 kilograms per square centimeter (16,000 pounds per square inch). At that pressure, an unprotected human being would be crushed to death. And yet, even in such a hostile environment there is life, including a primitive type of shrimp.

At lesser depths of the deep ocean, marine biologists have found hundreds of life forms, ranging from single-celled microorganisms to crabs, worms, and fish. There are no plants because there is no light to support photosynthesis, the process by which plants use the energy of sunlight to grow. Most of the food that sustains life at the bottom is organic debris that drifts down from the waters nearer the surface. Also, hydrothermal vents and cold seeps (areas where methane escapes from deeply buried deposits) support dense populations of specialized bacteria that live by chemosynthesis–the manufacture of nutrients from hydrogen sulfide or methane. Animals that live near the vents feed on these bacteria and on each other.

The Beginning of Deep-sea Exploration

The knowledge we currently have about the deep ocean has been a long time coming. The exploration of the deep ocean floor began in 1856, with the laying of the first telegraph cable across the Atlantic Ocean. To lay the cable correctly, it was necessary to make detailed depth measurements of the sea floor along the cable's 3,200-kilometer (2,000-mile) route between Newfoundland and the southwest corner of Ireland. These readings were made with a sounding line, a strong, thin cord with a heavy sinker at one end. The line was marked at regular intervals, like a giant measuring tape, to indicate depth.

The first major oceanographic expedition—for the sake of science rather than for commercial or military purposes—was made by the British naval ship HMS Challenger. From 1872 to 1876, the Challenger sailed the Atlantic, Pacific, Antarctic, and southern Indian oceans. Its scientists took water temperature readings at various depths, collected water for chemical analysis, dredged up samples of deep-sea sediment, much of it rich in plant and animal life, and made numerous soundings. The Challenger's voyage aroused interest in deep-sea exploration, and in the following years several countries, including Germany and the United States, launched oceanographic expeditions.

New Technologies Add to Knowledge of the Sea Floor

Deep-sea research got a boost with the invention of sonar in 1914. Developed to detect icebergs at night or in fog, sonar quickly proved to be an excellent depth-finder, much faster than the old sounding line. Sonar is based on the principle that sound travels through water at a rapid and fairly constant rate. A “pinger” mounted underwater on a ship's hull sends out periodic bursts of sound. The sound waves bounce off obstacles and get reflected back to the ship. By measuring how long it takes for the reflected waves to return to the ship, the distance to an obstacle can be calculated.

During World War I (1914–1918), Britain, France, and the United States refined sonar for use against German submarines. By the mid-1920's, most of the world's navies were equipped with sonar, and by the 1930's oceanographers were using it to map the sea floor. With experience, researchers learned that the speed of sound through seawater can be affected by changes in the water's temperature, pressure, and salinity (amount of salt), resulting in erroneous readings, so they worked out methods to correct these distortions. This refinement allowed oceanographers to accurately map portions of the sea floor. But because the ocean bottom is vast, only a small percentage of it could be mapped in this way.

In the 1930's, oceanographers also began adopting a technique called seismic reflection profiling, developed originally for use in oil exploration. In seismic reflection profiling, a large burst of sound is generated at the surface, and the sound waves that reflect from the ocean floor are picked up by an array of floating receivers. Originally, an explosive charge was used to create the sonic blast, but today a powerful air gun is used instead. Because the sound wave it produces is so strong, seismic reflection profiling not only reaches greater depths than sonar, it also penetrates sediments to give a true picture of the underlying bedrock.

Using Core Samples and Sonar Maps

Another frequently used exploration method is coring, which enables researchers to obtain cross-sections of sea-floor sediment. Coring is done by rapidly lowering a narrow, heavy, open-ended tube to the bottom. The tube plunges into the sediment and encloses a section of it. When the surface crew hauls the tube back up, a flap at the bottom end closes and prevents the sediment from falling out. Variations in the different layers of sediment reveal information about the history of the sea and of Earth's climate.

Core samples from bedrock are obtained by drilling into the rock, using equipment adapted from oil-well derricks. Drilling is done from special ships able to hold a constant position and equipped with sophisticated computers to guide the drill. The rock cores yield valuable insights into the geological history of the deep-sea floor and of the Earth itself. For example, drill cores from the Mid-Atlantic Ridge contained proof that the Earth's magnetic field periodically reverses. The evidence was in magnetic patterns frozen in bands of lava that had flowed from each side of the Atlantic rift and solidified.

Like sonar maps, most maps of the ocean floor based on coring and drilling are compiled from data gathered from widely spaced swaths of the sea floor. Thus, the information they provide is patchy. The most comprehensive pictures of the ocean bottom are made by satellite gravimetry. Satellites in orbit around the Earth send out radar signals to measure the varying height of the ocean surface. These small but detectable variations are caused by differences in the gravity of underwater features. Massive objects beneath the sea exert more gravitational force on the surrounding water than small features do. Therefore, an underwater mountain pulls more water toward itself, forming a hump on the surface that may be up to 60 centimeters (2 feet) higher than the surrounding sea. Over a deep trench, on the other hand, the water forms a shallow trough. The shape of the underlying sea floor can be calculated from these slight variations.

Submersible Vehicles Carry Researchers to the Depths

But satellites and drilling rigs don't normally come to people's minds when they think of deep-sea exploration. For most people, undersea research means going down to the ocean bottom in a manned submersible (undersea exploration vessel). And many oceanographers agree that observations made from the surface can go only so far. A manned submersible enables them to get close to whatever they want to observe and see it with their own eyes. It also permits them to collect exactly the samples they want to study.

A submersible named the Trieste I holds the deep-diving record: a descent to a depth of 10,912 meters (35,800.5 feet) in the Challenger Deep of the Mariana Trench. The Trieste was not a true submarine, however, but a bathyscaph (from the Greek words for deep and tub). Like a hot-air balloon, it was designed to travel up and down. Not coincidentally, it was designed by Auguste Piccard (oh GOOST pee KAHR), a famous Swiss designer of high-altitude balloons. The vehicle's cigar-shaped outer hull contained several large compartments filled with gasoline, which is lighter than water. For ballast, it carried some 8 metric tons (9 tons) of iron shot, attached to the hull by powerful electromagnets. To make the Trieste sink, the pilot released enough gasoline to lose buoyancy. To make it rise, he turned off one or more of the magnets long enough to drop the needed amount of ballast. The pilot and copilot sat in a pressurized steel sphere beneath the hull.

The Trieste made a series of successful dives beginning in 1953. On Jan. 23, 1960, it carried two men–Jacques Piccard, son of the inventor, and Lieutenant Don Walsh of the U.S. Navy—on the first-ever descent into the Challenger Deep. At the bottom of the trench, the men saw what appeared to be a bright-red shrimp and something they believed to be a type of flatfish. Most scientists, skeptical that fish could live at such a depth, insisted that the explorers had actually seen a strange type of creature known as a sea cucumber. Little information was gathered by the Trieste's dive—all Piccard and Walsh could do was sit in one place and observe—but it demonstrated that descending to the deepest parts of the ocean was possible.

Cousteau's Contribution

Long before the Trieste made its historic descent, scientists had discussed using small, maneuverable submersibles specifically designed for scientific observations to explore the ocean. It was Jacques-Yves Cousteau, coinventor of the original scuba-diving apparatus, who developed the first submersible used in undersea research. His little yellow Soucoupe Plongeante (Diving Saucer), launched in 1959, could carry two people to a depth of 300 meters (990 feet)—later increased to 410 meters (1,350 feet). The saucer's small size and maneuverability enabled it to travel along ridges and into canyons. Although a sphere is known to be the safest shape for a submersible's pressure hull, where its passengers ride, Cousteau opted for a flattened sphere for the Diving Saucer. This shape permitted the passengers to stretch out comfortably in a prone position rather than having to sit upright in a cramped spherical space.

Probably the world's most famous submersible is Alvin, operated by the Woods Hole Oceanographic Institution (WHOI) in Massachusetts. Alvin was launched in 1964, and was capable of diving 1,800 meters (6,000 feet). Its steel pressure hull was designed to carry a pilot and two scientists. Like all submersibles still operating, Alvin has been upgraded many times. Its newest hull, made of titanium, has a depth capability of 4,500 meters (14,750 feet).

Alvin has made many important dives. In the early 1970's, it took part in Project FAMOUS (French-American Mid-Ocean Undersea Study), a three-year study of the Mid-Atlantic Ridge in which oceanographers sampled, mapped, and photographed the gigantic undersea mountain range. In 1982, while investigating hydrothermal vents near the Pacific ridges, researchers on Alvin brought up the biological samples that turned out to be the mysterious Archaea.

The Drawbacks of Manned Submersibles

But submersibles have their limitations. For one thing, they are designed to travel at speeds of 1.6 to 5.6 kilometers (1 to 3.12 miles) per hour. This slow speed is sufficient for examining a small site, but it restricts a vehicle's range. Submersibles also take a long time to get to and from the sea floor. A typical dive may last six to eight hours, most of which is spent in vertical movement. Scientists become tired and uncomfortable after sitting in the cold, cramped pressure hull for several hours. Furthermore, the power supply of most submersibles is limited because they depend on batteries.

Expense is another limiting factor. Submersibles cost far too much to maintain and operate to simply go out and scour the ocean bottom, looking for interesting things. A submersible must be transported to a dive site aboard a surface ship, and another ship must first scout a proposed site with towed cameras and other instruments to make sure it is worth investigating firsthand. For example, a series of hydrothermal vents that Alvin visited in 1977 in the Pacific Ocean near the Galapagos Islands were first discovered by a towed temperature sensor, then double-checked with sonar, towed cameras, and laboratory analysis of water samples. Only then was the decision made to send Alvin down. Considering the work and expense involved with undersea exploration, it is not surprising that oceanographers often return to sites they have visited previously in order to study them more intensively. They are reluctant to visit a new site and come back with nothing.

Robotic Vehicles Gain In Favor

The great expense of operating manned submersibles led inevitably to the development of cheaper and simpler alternatives. One is the remote-operated vehicle (ROV). An ROV is powered by an electrical cable from a mother ship on the surface and is piloted by an operator on the ship. ROV's can be equipped with every type of instrument a manned submersible carries. Video cameras on the ROV transmit images of the ocean bottom to screens in the control room. ROV's are smaller than manned submersibles, so they can explore places like small caves and narrow crevices. And, unlike manned submersibles, they can be operated for extended periods, because they are powered by generators on the mother ship and because the operator is not confined inside the vehicle. ROV's are also much cheaper to build because—since they do not carry a crew—they do not need a costly, heavy pressure hull. They need only compact pressure cases to protect their instruments.

Some ROV's are carried partway down to the bottom by an underwater launcher that is towed by a ship on the surface. The launcher is equipped with video cameras and sonar that scan the sea floor as the ship cruises along. When the launcher detects a site of potential interest, the operator releases the ROV, which then examines the site in detail. This two-stage procedure enables oceanographers to explore a much larger area of the sea floor than they can with an ROV alone.

The Deepest Dive For A Robotic Vehicle

The deepest-diving ROV is Japan's Kaiko-10000, a $50-million craft built by the Japan Marine Science and Technology Center, a research institution backed by government and industry. Kaiko is an example of a two-stage ROV: a launcher 5 meters (17 feet) long carries a 3-meter (10-foot) roving vehicle most of the way to the bottom. Designed to operate as deep as 10,000 meters (32,800 feet), Kaiko has actually been even deeper than that. In March 1995, Kaiko was piloted into the Challenger Deep, reaching a depth just 0.6 meter (2 feet) short of the Trieste's record.

The Autonomous Underwater Vehicle

Another advance in undersea technology is the autonomous underwater vehicle (AUV). Like ROV's, AUV's are unmanned submersibles that must be transported to the dive site by a surface ship. Once it is in the water, though, an AUV operates independently, powered by batteries and controlled by a preprogrammed on-board computer. When its mission is completed, the AUV returns to the surface, where it deploys a buoy and a radio beacon so that it can be retrieved by its mother ship. An AUV named ROVER, operated by the Scripps Institution of Oceanography in La Jolla, California, crawls across sea-floor sediments on caterpillar treads and can function at depths up to 6,000 meters (19,700 feet). In 1996, ROVER descended to a depth of 4,100 meters (13,530 feet) some 200 kilometers (120 miles) off the coast of California to measure the oxygen consumption rate of organisms living in the top several centimeters of ocean-floor sediment. It gathered information that helped scientists estimate how much these creatures contribute to regulating the Earth's carbon supply, including the amount of carbon dioxide in the atmosphere.

A different type of AUV is WHOI's autonomous benthic explorer (ABE). The word benthic refers to the benthos, which is a technical term for the sea floor. Unlike ROVER, ABE is not a bottom crawler. Instead, it cruises above the bottom, taking photographs, water samples, or whatever else it has been programmed to do. In the summer of 1996, ABE gathered data on geomagnetism (the magnetic field generated by the Earth) on the Juan de Fuca Ridge off the coast of Oregon.

Like manned submersibles, ROV's and AUV's have their weaknesses. An ROV's cable can twist and malfunction or get snagged on obstructions on the bottom. The cable can also short out or snap, imperiling the crew on the deck of the surface ship. Also, AUV's are limited in the type of work they can do because they must be programmed in advance. If the vehicle encounters something unexpected, it cannot improvise as a human operator could. Furthermore, because working at sea is such an unpredictable enterprise, scientists who send an AUV out on a mission realize that the vehicle simply might not come back.

The Benefits of Deep-sea Exploration

Whatever means are used, exploration of the abyss promises a variety of benefits. Several projects are currently underway to study the potential of the deep ocean for scientific and medical research, mineral and fuel supplies, and the disposal of hazardous waste.

Investigations along the Mid-Ocean Ridge, for example, have helped geologists understand how the Earth's crust is formed, provided clues about the deep structure of the planet, and greatly increased our knowledge about the nature of the Earth's magnetic field. And biologists are discovering animal species–and in the case of the Archaea, an entirely new branch of life—that were unknown just decades ago.

The unique physiology of deep-sea organisms, which have adapted to conditions found nowhere else on Earth, has led scientists to study whether they may yield new medicines. An increasingly serious problem for society is the growing number of disease-causing bacteria that over time have developed a natural resistance to antibiotics. Researchers, therefore, are turning to marine organisms in search of new substances from which they can develop medicines to treat bacterial illnesses. Scientists are hopeful that bacteria would take many years to develop a resistance to drugs derived from deep-sea organisms.

A Vast Storehouse of Minerals

The ocean floor is also a vast storehouse of minerals. The most intriguing of these are manganese nodules, millions of which litter great swaths of the abyssal plains. Manganese nodules are metal-rich nuggets that range from half a centimeter to 25 centimeters (0.2 to 10 inches) in diameter. How they form is not fully understood. They consist chiefly of manganese but also contain iron, copper, cobalt, and nickel. Manganese is vital in making modern high-strength steels and other alloys. Cobalt and nickel, too, are used to make alloy metals. Manganese nodules could thus be an important source of some of these minerals. Several methods have been suggested for mining the nodules, including the use of remote-controlled, bottom-crawling robots.

Large concentrations of iron, silica (silicon dioxide, a common mineral), and other minerals, including gold, are known to exist in the deep ocean. But the value of these minerals is generally too small to justify the expense of retrieving them from the farther ocean depths.

Proposed Sea-floor Operations–and Environmental Concerns

Although the deep ocean floor may seem like an attractive source of metal ores, there are concerns about the possible harmful effects of sea-floor mining on marine ecology. For example, roughly 80 percent of the material brought up from the sea floor would be mud. After the valuable ore had been separated, the mud would be dumped back into the water, forming a large cloud of fine particles. This cloud would block light from plankton (microscopic marine organisms), which require sunlight to sustain themselves, resulting in massive die-offs of the microorganisms and disrupting the oceanic food chain. Because the sediment particles would be so fine, they could remain floating near the surface for months or years. And if ores were processed at sea, there is a risk that toxic wastes would be dumped into the water. Nonetheless, experts generally agree that the harmful effects of mining would affect only small areas of the ocean floor.

Oil is another important resource that the ocean floor may have in abundance. Offshore oil rigs have been drilling into the continental shelves—especially in the Gulf of Mexico and the North Sea—since the mid-1900's. Gradually, however, drilling operations have been moving into deeper waters. As of mid-1997, the deepest-drilling rigs operated in no more than 1,500 meters (5,000 feet) of water, but newer designs were in the works that would double that figure to 3,000 meters (10,000 feet). But if oil companies decide to drill for oil in the deepest parts of the ocean, completely new technologies will be required.

Like deep-sea mining, deep-sea drilling may also create ecological problems. Some experts warn that, as with any oil-retrieval operations, there would be a risk of breaks, leaks, and oil spills. Repairing such damage quickly at such depths would be extremely difficult.

Methane Under the Sea

Scientists are also studying the possibility of retrieving vast deposits of methane from the ocean floor. Methane, which ordinarily exists on Earth as a gas, burns more cleanly than coal or petroleum, and it may be an important fuel in the future. Methane is given off by the digestion process of bacteria living in ocean sediments. Scientists have found that the low temperature and extremely high water pressure at the sea floor traps methane in the form of methane hydrates (methane confined within ice crystals) in the sediment. Scientists drilling for sediment cores frequently hit pockets of methane hydrates. Nations like Japan, which have no oil of their own, are interested in tapping into these deposits, some of which are found off the Japanese coast.

But again, experts caution, the possible harmful effects on the environment would need to be examined. Methane is a powerful greenhouse gas (a gas that contributes to the warming of the atmosphere). If large quantities of methane were freed during the recovery process and allowed to escape into the atmosphere, there could be an unpredictable effect on the world's climate. Some scientists also suspect that the occasional melting of methane hydrate pockets causes huge underwater landslides, which in turn may trigger destructive tsunamis (huge waves caused by storms or underwater disturbances). Extracting methane from the sea might therefore contribute to even more landslides and tsunamis. Other scientists, however, say that the possible adverse consequences of mining methane hydrates have been exaggerated.

Using the Sea Floor As A Toxic Waste Dump

Another potential use for the deep-sea floor is the disposal of such dangerous materials as nuclear wastes and toxic chemicals. Some experts have proposed using sites near the middle of large, stable oceanic plates, deeply covered with sediment, for this purpose. One suggested disposal method is to drill a deep hole in the sediment, pump the waste down in the form of a slurry, and push the sediment back into the hole. The clay particles of oceanic sediment present a formidable barrier to the movement of waste. They also have a great ability to capture and bind radioactive particles, trapping them permanently and preventing them from getting into the environment. Another strategy calls for encasing nuclear waste in heavy, dart-shaped containers called flechettes, which would be dumped from ships at specially selected ocean locations. The flechettes, weighing 4.5 to 5.5 metric tons (5 to 6 tons), would strike the soft sea floor at a speed of about 160 kilometers (100 miles) per hour, penetrating it deeply. The walls of the resulting hole would quickly collapse inward, burying the flechette.

Looking to the Future

Most of these ideas for utilizing the deep sea have been around for many years. The idea of embarking on a new era of pioneering exploration—of the solar system as well as our own planet–—became extremely popular in the 1960's and early 1970's. While space scientists envisioned colonies in orbit and on the moon, many oceanographers championed an “undersea NASA” effort to develop colonies on the ocean floor. But all these ideas fell victim to cuts in government funding in the 1970's. In the 1990's, however, the idea of exploring the deep ocean grew more popular again.

A potential new breed of manned submersibles was under development in California in the 1990's. An engineer named Graham Hawkes in 1996 successfully tested Deep Flight I, a prototype of a one-man submersible of revolutionary design, and Deep Flight II was in the planning stage. Instead of descending vertically to the sea floor, Deep Flight II would “fly” down, guided by winglike control surfaces. Deep Flight II's expected top speed of 22 kilometers (14 miles) per hour would enable it to reach the bottom quickly and cover a great deal of territory. Thus, it could be useful for undersea exploration and photography.

Progress toward a permanent underwater base took a step forward in September 1996, with the installation of an unmanned facility called LEO-15 (for Long-term Ecosystem Observatory in 15 meters [50 feet] of water) in the Atlantic Ocean. LEO-15, a joint project of researchers and engineers from WHOI and Rutgers, the State University of New Jersey, is fastened to the sea floor at that depth off the coast of New Jersey. The observatory consists of two racks of instruments, each assembly surrounded by an outer shell of treated stainless steel secured to the sea floor by anchors. LEO-15 is intended to serve as a base for ROV’s and for experiments that can be operated remotely by scientists anywhere in the world. While it is small and not designed for human habitation, LEO-15 takes advantage of computer technology to create a kind of virtual human presence in the ocean. Shallow-water experiments like LEO-15 may lead to similar projects at ever-greater depths.

In many ways, the course of deep-ocean exploration may parallel that of space exploration. Robotic vehicles have been investigating the solar system for decades, and in 1997, two U.S. space probes were scheduled to make the first visit to the planet Mars in more than 20 years. Closer to home, the Hubble Space Telescope has become a successful observatory in orbit, while the Russian space station Mir and the United States space shuttles have taken the first steps toward a permanent human presence in space. Similarly, the exploration of “inner space” will most likely involve the continued use of both manned and unmanned vehicles to explore the deep ocean in detail and of satellite and solar imagery to map the sea floor on a wide scale. One day, these explorations could progress to the point where human beings might live and work in a permanent “inner-space station” beneath the sea.