A NOAA Ocean Exploration remotely operated submersible vehicle encountered a strange golden sphere at a depth of about 3,300 meters (2 miles) below the ocean surface off the coast of Alaska, where warm sunlight never penetrates.

The strange underwater object, discovered during last year’s expedition, was “firmly attached” to a rock decorated with white sponges, measuring about 10 centimetres (4 inches) in diameter and having a hole on one side.

It wasn’t clear to the scientists who made the discovery what exactly this mysterious ball was. The researchers, who live-streamed the dive, initially speculated that it contained the eggshell of a mysterious species, a dead sponge or coral.

“I hope when we drill into it nothing comes out,” one researcher said. “It’s like the beginning of a horror movie.”

As profound a horror as it is, perhaps it still has room to grow. According to The Guardian , one hypothesis suggests that something has already emerged from the golden box. Something not exactly small.

“We think it’s an egg because of its texture. It looks fleshy and there’s no obvious anatomy. There’s a hole that shows something going in and out. But it’s unlike any egg I’ve ever seen,” Kerry Howell, a deep-sea ecologist at the University of Plymouth in Great Britain, told the newspaper.

“If it’s an egg, the interesting question is whose egg it is. It’s quite large. This is not a small fish egg. This is something important.”

The researchers gently prodded the object using a robotic arm to determine that it was soft enough, then used suction to collect it for further study. The fact that the “egg” is solitary is almost as intriguing as its size. Egg-laying animals typically lay their eggs in clutches.

So if the object is an egg, there’s something unusual about it. And that’s really cool: Whatever it is, the sphere could tell us something new about the deep ocean and the diverse life that thrives there.

There’s a lot going on in the inhospitable ocean depths that we don’t yet understand. Crushing pressure and low temperatures are just two of the factors that have prevented humanity from fully exploring the ocean depths.

But thanks to remote-controlled proxies, the ocean is slowly revealing its secrets—including how mysterious deep-sea species reproduce.

“Isn’t it strange out there in the deep sea?” said Sam Candio, research coordinator for NOAA Ocean Exploration. “We collected the ‘gold ball’ and brought it back to the ship, but we still can’t identify it beyond its biological origin.

“While this discovery is somewhat humbling, it is a reminder of how little we know about our own planet and how much we still have to learn and appreciate about our ocean.”

A previous version of this article was published in September 2023.