(ITO) Ocean Exploration Lesson

Ocean Exploration

Planet Earth is not an especially large planet, but there are vast areas of the planet that we have not yet explored. The vast majority of these areas are under our oceans. By exploring the ocean, we can learn more about the oceans that cover approximately 75% of our planet. Once we are equipped with this knowledge (and we may never learn all there is to know), we can focus on protecting our oceans and using the knowledge we do have to ensure that the oceans are preserved for many years to come. 

Challenges

Exploring the ocean is not as easy as exploring the land. For one, we cannot breathe under the ocean. Any exploration done by humans has to include a way for the scientists to breathe while studying the oceans.

For shallow depths, this can include SCUBA, Self Contained Underwater Breathing Apparatus, that allows divers to breath underwater and physically explore the ocean. For deeper depths, humans can only descend if they are in a submersible, a type of small submarine, because of one of the other challenges of ocean exploration: the crushing pressures found at increasing depths of the ocean.

At sea level, the air in the atmosphere pushes down on our bodies at 14.5 pounds per square inch (psi). This 14.5 psi is known as "1 atmosphere" or "atm". However, the ocean water is much more dense than air, so it presses down   much more than air. For every 33 feet you descend into the ocean, the pressure increases an additional 14.5 psi or 1 atmosphere. This means if you descend merely 100 feet down, you will already be over 3 atmospheres, which means that the pressure pushing down on you is over 3 times the pressure you experience at the surface. The very deepest part of the ocean is 6.83 miles or 36,062 feet. This translates to over 1092 atms!! That amount of pressure can easily crush most living things and equipment. This means that in order for equipment explore the bottom of the ocean, it must be built strong enough to withstand the massive pressure at the bottom of the ocean.  

The bottom of the ocean is incredibly cold. As the depth of the ocean increases, the temperature decreases until it reaches about 0-3 degrees Celsius (32-37.5 degrees Fahrenheit! Because the water is so salty, it does not freeze. Because it is so cold at the bottom of the ocean, any equipment that descends past approximately 1500 meters must be designed to work in very cold environments. If a submersible is carrying scientists to the deep ocean, it must be designed with heating systems to keep the people inside warm enough that they do not get too cold.

The ocean covers most of our planet. This means that a large part of the ocean is not close to major land masses. If scientists want to explore the deepest, most remote parts of the ocean, they cannot do this from land. They must use a specially-designed research vessel to launch their equipment and/or missions. Because these missions are based off of ships, they are subject to weather and wind like any other ship and missions can often get cancelled because the weather or waves are too dangerous to launch equipment from the ship.

The bottom of the ocean is also very dark. This is because light can only penetrate the first 1000 meters of the ocean and significant light is rarely seen below 200 meters. Therefore, any equipment or people (in submersibles) that travel below this depth must be equipped with very bright lights in order to see anything and send back useful videos and images.

As you can see, very advanced equipment is required to visit the bottom of the ocean. This equipment is costly to build and maintain. Additionally, this equipment must be powered by something. Many undersea research vessels are powered by a very, very long cable that delivers power to the vessel. If the vessel does not have a cable, it must have an onboard power source powerful enough to power the trip down, collect samples and explore, and power the trip back to the surface, which adds additional expense to the mission.

Lastly, the seawater is very corrosive. This means that metals and equipment will quickly rust and wear out if left in the water for any amount of time. Equipment that is put in the ocean for many days, months, or years must be made of a material that will not rust or corrode. Usually this means that the metal parts of the equipment are located inside some sort of plastic housing or the metal is rustproof.

Because of all of these challenges, only 4 people have ever visited the deepest part of the ocean: Challenger Deep, Mariana Trench in the Pacific Ocean. In 1960, Jacques Piccard and Don Walsh descended for over 5 hours to reach Challenger Deep. No one else was able to make it back until in 2012, when film director James Cameron descended for over 2 hours to visit Challenger Deep. He chronicled his voyage in the movie, Deepsea Challenge. Most recently, in May 2019, Victor Vescovo journeyed to the bottom of Challenger Deep as part of his Five Deeps mission to visit the deepest part of each ocean.

Technology

Technology used to explore the ocean is not one size fits all. Different types of technology are better for different tasks. There are several primary types of technology used to study our oceans: buoys and water column samplers, coring devices, ROVs, HOVs, sonar, trawls, and satellites.

Buoys and water column samplers are useful for monitoring sea surface conditions and water quality. Depending on the device, it can measure salinity, plankton, weather, temperature, the shape of the seafloor, the speed of currents, conductivity, and a myriad of other factors. Not every buoy and sampler can measure all of these components at once, so a scientist will choose the device that best fits his or her needs. Some of these devices are designed to sit at the surface in one spot and continually collect data, like weather buoys, and some are designed to travel deep into the ocean and collect data from different areas under the surface of the ocean.

Coring devices are used to collect sediment samples. These samples can be used to help us understand ancient oceans and Earth.

SONAR stands for SOund NAvigation and Ranging. Sonar uses sound to find and identify objects underwater. It is also frequently used to determine the depth of an area of the ocean.

ROVs are remotely operated vehicles. These allow scientists to safely and efficiently explore all parts of the ocean. These vehicles are much cheaper, efficient, and safer than manned submersibles, so exploration is shifting away from manned missions and towards unmanned ROVs.

One of the most accomplished ROVs is the team of Jason and Medea. This pair of ROVs can descend up to 10 km (6 miles) below the ocean floor. They are tethered to their ship by a long cable that delivers power and they return data and live video imagery. Medea is a shock absorber and travels behind Jason. She also provides lights and an "aerial" view of Jason, so the scientists controlling the submersibles can see Jason. Jason is equipped with sonar, video, and still imaging systems, lights, and sampling systems. Jason was first launched in 1988 and has been updated several times since. Interestingly, Jason Jr was used to survey the wreck of the RMS Titanic.

HOVs are similar to ROVs except they are human occupied vehicles. This means that they allow a human to ride inside them and study the ocean. The three most famous HOVs are Alvin, Deepsea Challenger, and Pisces V. Pisces V can hold 3 people and descend down to 6500 feet.

Alvin was first commissioned in 1964 and holds two scientists. He can descend down to 4500 meters and dives in Alvin can last up to 10 hours. 

Deepsea Challenger is the one-person submersible that James Cameron took to Challenger Deep in 2012. This HOV is rated for the full depth of the ocean and is 7.3 meters (24 feet) long. 

Trawling nets are pulled behind research vessels. These are similar to the nets used to catch fish and shellfish. These nets can descend to great depths, where they scrape along the seafloor and bring back organisms they've collected from the seafloor for study. These nets can cause extreme habitat destruction, but they were one of the first ways that scientists had to study the organisms that live in the deep ocean.

Finally, satellites orbiting the planet in space can be used to observe Earth's atmosphere, lands, and oceans.

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