Mystery 'Alien' Holes Discovered on Seafloor, 8,300ft Below Ocean Surface

Ocean scientists have discovered a number of mysterious holes in the seafloor that look human-made despite being located 2,540 meters (8,333 feet), or 1.6 mile underwater.

The holes were discovered during Dive 04 of the National Oceanic and Atmospheric Administration's (NOAA) second Voyage to the Ridge 2022 expedition, which seeks to gather data on unexplored deepwater regions in the Atlantic Ocean such as the Mid-Atlantic Ridge.

Photos show how the holes are arranged in a straight line and appear to all be a similar distance apart.

Another notable characteristic of the holes is that they all appear to be surrounded by small piles of sediment, suggesting they had been excavated.

Holes in ocean floor
An NOAA photo of the holes found in the ocean floor, 1.6 miles underwater. The origin of the holes is unknown. NOAA Ocean Exploration, Voyage to the Ridge 2022

The NOAA scientists were so puzzled that they took to social media to see if members of the public had any hypotheses they could put forward.

"I think it is a minor crack in the surface which allowed gasses to escape," wrote one Facebook user. "I would say starfish doing cartwheels," wrote another.

Another Facebook user said they thought the cause was "either an alien craft, or an underwater craft probably illegally searching for something under the sand."

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The NOAA wrote in a news release: "We got a variety of responses, from aliens to an unknown crab species to gas rising up from below the seafloor and more."

It's not the first time holes like this have been discovered. Scientists noticed a similar phenomenon during a dive along the Mid-Atlantic Ridge back in July 2004, at a depth of around 6,800 feet.

At that time, two marine scientists, Michael Vecchione from the U.S. National Marine Fisheries Service and Odd Aksel Bergstad from the Institute of Marine Research in Norway, put forward the theory that the holes were made by an organism living in the sediment or perhaps the feeding appendage of a larger animal. The two researchers named the holes "lebensspuren," or "life traces."

Holes in ocean floor
The mysterious underwater holes seen from another angle, showing how they appear to be arranged in a straight line. NOAA Ocean Exploration, Voyage to the Ridge 2022

In any case, the origin of the holes is still unknown. For the researchers, it highlights how there are still gaps in our basic understanding of mid-ocean ridge ecosystems.

The Voyage to the Ridge 2022 expedition has been running since May and is due to conclude in September. As part of the research, marine scientists use robotic vehicles that can dive to depths of up to 6,000 meters, or nearly 20,000 feet, deep.

"During dives, we expect to explore deep-sea coral and sponge habitats, potential hydrothermal vent and extinct polymetallic sulfide systems, fracture and rift zones, and the water column," the NOAA states. Dives are streamed daily.

Spanning the north-south length of the Atlantic Ocean for around 10,000 miles, the Mid-Atlantic Ridge is the longest mountain range in the world yet it remains largely unexplored. The area is seismically active, with frequent earthquakes. There are also hydrothermal vents, providing warm areas known to support diverse organisms.

Other areas for research within the expedition include the Charlie-Gibbs Fracture Zone and the Azores Plateau.