Oceans cover more than 70% of Earth's surface, yet over 80% of them remain unexplored by humans.

In fact, our understanding of the surfaces of Mars and the Moon surpasses what we know about the deep ocean. NASA, known for its space exploration, has embarked on a deep-sea exploration initiative to bridge this gap.

The aim is to uncover the mysteries of Earth's deepest oceans, which might provide insights into the oceans of other planets, and to push the limits of human technological capabilities in extreme environments. This mission is full of wonders but also fraught with dangers, as the immense water pressure poses a significant risk of catastrophic failure.

NASA hopes that discoveries from deep-sea expeditions will unlock secrets of outer space while also testing equipment and experiments needed for interplanetary exploration. Earth's deepest oceans and the environments of certain planets within the solar system share striking similarities. Exploring these depths could guide scientists on where to look for extraterrestrial life.

The Hadal Zone: Earth's Deepest Abyss

The Hadal Zone, named after Hades from Greek mythology, is the deepest part of Earth's oceans. This forbidding region consists of trenches and basins, plunging to depths of up to 11 kilometers below sea level. Its total area is equivalent to that of Australia. Only a handful of submersibles have dared to venture into this shadowy abyss.

In this dark region, NASA scientists collaborate with the Woods Hole Oceanographic Institution (WHOI) to study the limits of life on Earth. Interestingly, the terminology used for deep-sea exploration often mirrors that of space exploration. For example, marine biologists use sensor-equipped "landers" to "crash-land" in these uncharted depths to conduct measurements.

NASA's Jet Propulsion Laboratory (JPL) in Southern California is developing a new autonomous deep-sea robot named Orpheus, inspired by the Greek hero who ventured into the underworld. Orpheus uses visual navigation technology similar to NASA's Perseverance Mars Rover, employing highly sensitive cameras to identify features such as rocks and shells on the ocean floor. These features help create a 3D "map of the seabed," enabling the robot to navigate independently and recognize previously explored areas. This technology may also help discover new life forms adapted to these extreme conditions.

Tim Shank, a deep-sea biologist leading WHOI's exploration program, believes Orpheus represents a significant leap forward. "If successful," he said, "there will be no part of the ocean humanity cannot reach."

Orpheus's predecessor, Nereus, was sent to the Kermadec Trench near New Zealand in 2014 but exploded under immense water pressure at a depth of 10 kilometers. Lessons learned from Nereus's failure have informed the design of Orpheus, which is about the size of a bicycle, weighs 250 kilograms, and is lighter and more cost-effective than previous submersibles. Its lightweight build enables it to reach previously inaccessible trenches and hydrothermal vents on the ocean floor.

Discoveries Beneath the Ocean's Surface

For a long time, scientists believed the Hadal Zone was devoid of life. It was thought that all marine life depended on the food chain sustained by photosynthesis, with dead organic material sinking from surface waters to feed life at the bottom. However, in 1977, the Alvin submersible uncovered vibrant ecosystems around hydrothermal vents at a depth of 2,440 meters in the Pacific Ocean. These ecosystems thrived not on sunlight but on chemicals emitted from the Earth's interior.

Lifeforms in these depths have evolved to withstand pressures of up to 15,000 pounds per square inch. They achieve this through a unique substance called piezolytes, which prevent cell membranes and proteins from being crushed. This groundbreaking discovery has raised the possibility of finding similar life forms in the oceans beneath the icy surfaces of celestial bodies like Europa, one of Jupiter's moons.

Oceans on Other Worlds

Europa's subsurface ocean, believed to be 60-150 kilometers deep, contains twice as much water as Earth's oceans. Despite its thick ice shell, the environment below might be similar to Earth's Hadal Zone. NASA scientists are optimistic that robots like Orpheus, capable of withstanding extreme pressures and temperatures, could one day explore these extraterrestrial oceans.

The Subsea program, launched by NASA in 2017, combines space and ocean exploration. It has already completed missions to underwater volcanic sites off the coasts of Hawaii and California, which are considered analogous to the conditions beneath the icy shells of Europa and Enceladus, Saturn's moon.

Connecting Space and Ocean Exploration

The challenges of deep-sea exploration mirror those of space missions. Robots deployed to both environments must be fully autonomous, capable of decision-making, and equipped to endure extreme conditions. For instance, Orpheus's synthetic foam hull is designed to withstand crushing pressures, a feature adapted from James Cameron's Deepsea Challenger submersible.

Deep-sea exploration also informs NASA's efforts to explore the Moon and beyond. The upcoming Viper mission will send a rover to the Moon's South Pole to search for water ice. Lessons learned from Subsea have been instrumental in preparing for such missions.

NASA's dual focus on space and ocean exploration not only advances human understanding of the cosmos but also provides critical insights into Earth's own uncharted territories. As Laura Lorenzoni, a NASA ocean biogeochemist, emphasizes, "If we want to save the oceans, we must understand them." Through these efforts, humanity takes steps toward unraveling the mysteries of both the stars above and the depths below.