Anne Marie Helmenstine

Oceans cover 70 percent of the Earths surface， yet even today their depths remain largely unexplored. Scientists estimate between 90 and 95 percent of the deep sea remains a mystery. The deep sea is truly the planets final frontier.

What Is Deep Sea Exploration？

The term “deep sea” doesnt have the same meaning to everyone. To fishermen， the deep sea is any part of the ocean beyond the relatively shallow continental shelf. To scientists， the deep sea is the lowest part of the ocean， below the thermocline （the layer where heating and cooling from sunlight ceases to have an effect） and above the sea floor. This is the part of the ocean deeper than 1，000 fathoms or 1，800 meters.

Its difficult to explore the depths because they? ?are? ?eternally①?; ?dark，? ?extremely? ?cold

（between 0℃ and 3℃ below 3，000 meters）， and under high pressure （15，750 psi or over 1，000 times higher than standard atmospheric pressure at sea level）. From the time of Pliny until the end of the 19th century， people believed the deep sea was a lifeless wasteland. Modern scientists recognize the deep sea as the largest habitat on the planet. Special tools have been developed to explore this cold， dark， pressurized environment.

Deep sea exploration is a multi-disciplinary endeavor that includes oceanography， biology， geography， archaeology， and engineering.

A Brief History of Deep Sea Exploration

The history of deep sea exploration begins relatively recently， mainly because advanced technology is needed to explore the depths. Some milestones include：

1521： Ferdinand Magellan attempts to measure the depth of the Pacific Ocean. He uses a 2，400-foot weighted line， but does not touch bottom.

1818： Sir John Ross catches worms and jellyfish at a depth of approximately 2，000 meters （6，550 feet）， offering the first evidence of deep sea life.

1842： Despite Ross discovery， Edward Forbes proposes the Abyssus Theory， which states biodiversity decreases with death and that life cannot exist deeper than 550 meters （1，800 feet）.

1850： Michael Sars refutes② the Abyssus Theory by discovering a rich ecosystem at 800 meters （2，600 feet）.

1872-1876： The HMS Challenger， led by Charles Wyville Thomson， conducts the first deep sea exploration expedition. Challengers team discovers many new species uniquely adapted to life near the sea floor.

1930： William Beebe and Otis Barton become the first humans to visit the deep sea. Within their steel Bathysphere， they observe shrimp and jellyfish.

1934： Otis Barton sets a new human diving record， reaching 1，370 meters.

1956： Jacques-Yves Cousteu and his team aboard the Calypso release the first full-color， full-length documentary， Le Monde Du Silence （The Silent World）， showing people everywhere the beauty and life of the deep sea.

1960： Jacques Piccard and Don Walsh， with the deep sea vessel Trieste， descend to the bottom of the Challenger Deep in the Mariana Trench （10，740 meters）. They observe fish and other organisms. Fish were not thought to inhabit such deep water.

1977： Ecosystems around hydrothermal vents are discovered. These ecosystems use chemical energy， rather than solar energy.

1995： Geosat satellite radar data is declassified， allowing for global mapping of the sea floor.

2012： James Cameron， with the vessel Deepsea Challenger， completes the first solo dive to the bottom of the Challenger Deep.

Modern studies expand our knowledge of the geography and biodiversity of the deep sea. The Nautilus exploration vehicle and NOAAs Okeanus Explorer continue to discovery new species， unravel mans effects on the pelagic③ environment， and explore wrecks and artifacts deep beneath the sea surface. The Integrated Ocean Drilling Program （IODP） Chikyu analyzes sediments from the Earths crust and may become the first ship to drill into the Earths mantle.

Instrumentation and Technology

Like space exploration， deep sea exploration requires new instruments and technology. While space is a cold vacuum， the ocean depths are cold， but highly pressurized. The saltwater is corrosive④ and conductive. Its very dark.

Finding the Bottom

In the 8th century， Vikings dropped lead weights attached to ropes to measure water depth. Beginning in the 19th century， researchers used wire rather than rope to take sounding measurements. In the modern era， acoustic depth measurements are the norm. Basically， these devices produce a loud sound and listen for echoes to gauge⑤ distance.

Human Exploration

Once people knew where the sea floor was， they wanted to visit and examine it. Science has progressed way beyond the diving bell， a barrel containing air that could be lowered into the water. The first submarine was built by Cornelius Drebbel in 1623. The first underwater breathing apparatus was patented by Benoit Rouquarol and Auguste Denayrouse in 1865. Jacques Cousteau and Emile Gagnan developed the Aqualung， which was the first true “Scuba” （Self Contained Underwater Breathing Apparatus） system. In 1964， Alvin was tested. Alvin was built by General Mills and operated by the US Navy and Woods Hole Oceanographic Institution. Alvin allowed three people to remain underwater for as long as nine hours and as deep as 14，800 feet. Modern submarines can travel as deep as 20，000 feet.

Robotic Exploration

While humans have visited the bottom of the Mariana Trench， the trips were expensive and only allowed limited exploration. Modern exploration relies on robotic systems.

Remotely Operated Vehicles （ROVs） are tethered vehicles that are controlled by researchers on a ship. ROVs typically carry cameras， manipulator arms， sonar equipment， and sample containers.

Autonomous Underwater Vehicles （AUVs） operate without human control. These vehicles generate maps， measure temperature and chemicals， and take photographs. Some vehicles， such as the Nereus， act as either a ROV or AUV.

Instrumentation

Humans and robots visit locations but dont remain long enough to collect measurements over time. Undersea instruments monitor? ?whale  ?songs，? ?plankton⑥? ?density，

temperature， acidity， oxygenation， and various chemical concentrations. These sensors may be attached to profiling buoys， which drift freely at a depth of about 1，000 meters. Anchored observatories house instruments on the seafloor. For example， the Monterey Accelerated Research System （MARS） rests on the floor of the Pacific Ocean at 980 meters to monitor seismic faults.

注：① eternally 永恒地

② refute 駁斥;反駁

③ pelagic 公海的

④ corrosive 腐蝕性的

⑤ gauge 測量

⑥ plankton 浮游生物