One of the main characteristics of Earth is that it is predominantly covered by water. Because the Earth’s oceans are so vast there is still much that scientists are trying to learn about them. The oceans are divided into four zones that are described by the amount of light they receive. The Sunlight zone is the uppermost layer, and since it absorbs the most sunlight, it supports the most abundant source of marine plant and animal life. It is also the zone that scientists have been able to study most easily. Below the Sunlight zone comes the Twilight zone, the Midnight zone, and finally the Abyssal zone. As the depths of these zones increase, their light source decrease to no light at all. What lies deep in the dark ocean has called to scientists for years. Unfortunately, it wasn’t until recently that scientists had access to tools like submersible drones that would allow them to study the lower zones of the ocean, particularly the Twilight zone.

At depths of 650 to 3,300ft, the Twilight zone is cold with very little light. Yet it still has a vast marine life, most of which produce their own light through bioluminescence. The animals that live in the Twilight zone range in size from microscopic to some of the largest creatures on the planet. One such creature, the giant squid, has long been a subject of fascination for oceanic scientists. The very shy creatures can grow up to 40ft long, have the largest eyeball in the world, and have mostly eluded observation. In 2002, a giant squid was photographed and captured as it came near the water surface off the shore of Goshiki Beach, Japan. In 2004 Japanese zoologist Tsunemi Kubodera was finally able to get more photographic evidence of a giant squid. It took him 2 years of searching, tons of bait to lure the creature close to the surface, and more than 20 attempts before he was able to bring the squid in close enough to photograph it.

Several years later a film crew captured live video footage of a giant squid off the Gulf of California by releasing a Humboldt squid with cameras attached to it. The goal was to get footage of a giant squid in its natural habitat. The expedition was led by Scott Cassell in 2006 and was aired as part of a documentary called MonsterQuest: Giant Squid Found. However, experts argued that the documentary presented inaccurate information and even Cassell has tried to distance himself from the project. Then finally, in 2019, a mission sponsored by the National Oceanic & Atmospheric Association (NOAA) was able to truly study a giant squid in the wild with the help of a specially designed drone.

The mission was called Journey into Midnight: Light and Life Below the Twilight Zone and was led by biologists Edith Widder and Nathan J. Robinson with a team of researchers from around the world with the use of an underwater drone named “Medusa”. The team launched the drone into the Gulf of Mexico’s Twilight zone, remotely operating it to a depth of 2,490 ft while tethered to the ship on the surface. The tether provided the drone with a power source and ensured it wouldn’t go beyond its maximum dive range of 6,560 ft. What sets the Medusa apart from other ROVs is the camera’s lighting system. Most underwater cameras use bright white lights to navigate and explore the dark depths of the ocean. Unfortunately, these bright lights can scare away creatures, especially a shy one like a giant squid. Often they are lucky enough to catch a quick glimpse after happening upon a creature before it hurries off. These drones also tend to use thrusters that scare off the creatures.

The Medusa uses red light that is invisible to the creatures living in the Twilight zone, and since it is powered through the tether it doesn’t rely on powerful jets or thrusters to move about. It can stealthily glide through the water, blending into the habitat. To further entice creatures towards the drone, the team baited it and outfitted it with an additional mimicry feature. Dangling off the front of the camera was a special light that would mimic the light given off by a bioluminescent creature, like a jellyfish. The fake bioluminescent lure on the drone worked flawlessly. Out of the darkness of the water, the drone’s camera suddenly picks up a massive squid coming at it, tentacles first. As the squid pulses its body to push forward, the tentacles spread wide into a starburst shape and you can see into its beak. Then the squid grasps onto the bioluminescent lure with a tentacle. Within seconds, the squid is able to taste through the suckers on its tentacle that the lure and drone are not edible, and it zooms off.

Professor Justin Marshall from The University of Queensland, a researcher with the mission explained just how phenomenal the footage captured by the Medusa was for science. Until this point, all other drone missions were simply unsuccessful at getting close enough to gather solid data. The bait on board the Medusa proved that giant squids can smell for some distance, as it was a strong enough scent to draw the squid in. It proved that the use of red light would work for further study, allowing researchers to see in low light zones without scaring off creatures. It also showed just how well a bioluminescent lure can unobtrusively attract creatures of interest. As Professor Marshall stated, “Almost everything we know about deep-sea animals is from catching them and bringing them on board a boat…But video of these remarkable creatures, alive and in their natural habitat, tells us so much more about them, their characteristics and habits than we knew previously.” With further use of submersible drones, scientists hope to better understand the ocean’s depths and how they impact the rest of the world.

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