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Deep Sea Exploration
Here's How We
Learn About the Deep Sea
by Anne Marie
Helmenstine, Ph.D.
Oceans cover 70 percent of the Earth's 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 planet's final frontier.
What Is Deep Sea Exploration?
The term "deep sea" doesn't 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.
It's difficult to explore the depths because they are eternally
dark, extremely cold (between 0 degrees C and 3 degrees C below 3,000
meters), and under high pressure (15750 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 refutes 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. Challenger's 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 (.85 miles).
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/6.67 miles). 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 NOAA's Okeanus Explorer continue
to discovery new species, unravel man's effects on the pelagic environment,
and explore wrecks and artifacts deep beneath the sea surface.
The Integrated Ocean Drilling Program (IODP) Chikyu analyzes sediments from the Earth's crust
and may become the first ship to drill into the Earth's 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 corrosive and conductive. It's
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 gauge
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
14800 feet.
Modern submarines can travel as deep as 20000 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 don't remain long enough
to collect measurements over time. Undersea instruments monitor whale songs,
plankton density, temperature, acidity, oxygenation, and various chemical
concentrations.
These sensors may be attached to profiling buoys, which drift
freely at a depth of about 1000 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.
Deep Sea Exploration Fast Facts
· The deepest part of the Earth's oceans is the Challenger Deep in
the Mariana Trench, at 10,994 meters (36,070 feet or nearly 7 miles) below sea
level.
· Three people have visited the depths of the Challenger Deep.
Film director James Cameron reached a record depth of 35,756 feet in a solo
submersible dive in 2012.
· Mount Everest would
fit inside the Mariana Trench, with over a mile of extra space above it.
· Using bomb sounding (throwing TNT into a trench and recording
the echo), scientists have found the Mariana Trench, Kermadec, Kuril-Kamchatka,
Philippine, and Tonga trenches all exceed 10000 meters in depth.
· While human exploration still occu rs, most modern discoveries
are made using data from robots and sensors.
Anne
Marie Helmenstine, Ph.D.
Introduction
Ph.D. in
biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge
National Laboratory.
Science
educator with experience teaching chemistry, biology, astronomy, and
physics at the high school, college, and graduate levels.
ThoughtCo
and About Education chemistry expert since 2001.
Widely-published
graphic artist, responsible for printable periodic tables and other
illustrations used in science.
Experience
Anne
Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education
since 2001, and other sciences since 2013. She taught chemistry, biology,
astronomy, and physics at the high school, college, and graduate levels.
She has worked as a research scientist and also abstracting and indexing
diverse scientific literature for the Department of Energy.
In
addition to her work as a science writer, Dr. Helmenstine currently serves as a
scientific consultant, specializing in problems requiring an interdisciplinary
approach. Previously, she worked as a research scientist and college
professor.
Education
Dr.
Helmenstine holds a Ph.D. in biomedical sciences from the University of
Tennessee at Knoxville and a B.A. in physics and mathematics with a minor
in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine
developed ultra-sensitive chemical detection and medical diagnostic tests.
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