In late summer 2023, a strange “golden sphere” discovered at the bottom of the Gulf of Alaska by a team from the National Oceanic and Atmospheric Administration (NOAA) had ignited the imagination of the public and scientists. Sticking to a rock outcropping about 3,250 meters deep, this smooth, golden, hole-pierced object was unlike anything obviously known. Nearly three years later, the mystery is finally solved, NOAA revealed on Wednesday April 22.
During the Seascape Alaska 5 expedition dives, the remotely operated underwater vehicle Deep Discovererdeployed from the ship Okeanos Explorespotted this small golden dome firmly attached to a rock. At the time, hypotheses exploded on the radio: a giant egg, a dead sponge, the remains of an unknown organism, even a shell abandoned by a creature that had escaped. Intrigued, the researchers sucked the object up using a suction system to bring it back on board, then sent it to the United States National Museum of Natural History in Washington for in-depth analysis.
Identifying this golden sphere proved much more difficult than expected. Allen Collins, zoologist and director of NOAA’s National Systematics Laboratory, initially thought that standard procedures would be enough to lift the veil. Very quickly, it became apparent that the case would require a targeted investigation involving morphology, genetics, deep-sea expertise and bioinformatics.
The first observations under the microscope showed that the object did not have classic animal anatomy: no obvious structures, but a fibrous material, with a stratified surface, loaded with stinging cells, signs of belonging to the phylum Cnidarians, the animal group including sea anemones, jellyfish and corals. Specialist Abigail Reft identified these cells as spirocysts, a type of cnidocyte specific to Hexacorallia. In short: a sea anemone or a close relative. A similar specimen collected in 2021 in another expedition showed the same cellular structure, reinforcing this hypothesis.
“Madam! You forgot your cuticle
Genetics first added to the confusion: an initial DNA reading proved inconclusive, probably because the fragment also bore the imprint of microorganisms living on its surface. The researchers then took the analysis further with complete genomic sequencing, which confirmed the presence of animal DNA and uncovered a high proportion of genetic material from a large deep-sea anemone. By sequencing the mitochondrial genome of this strange sphere, they noted near identity with the reference genome of Relicanthus daphneae.
Relicanthus daphneae is a giant anemone of the abyss, already observed notably during an expedition carried out in 2016 in the region of the Mariana Islands aboard theOkeanos Explore. In this marine animal, the visible part is only the crown of tentacles: the base, thick and solid, serves as an anchor on the rock and usually remains hidden from view. The golden sphere recovered corresponds precisely to this base, or rather to its “cuticle” left in place, the rest of the sea anemone having either perished or migrated to a new support.
Beyond the anecdote, these discoveries have concrete implications. Better understanding the biodiversity of the abyss can lead to advances in medicine, energy or biotechnology, as well as clarify choices for the protection and management of these still largely unexplored ecosystems. This is one of the goals of the Seascape Alaska campaign: to modernize and document the U.S. seabed off Alaska to support research, resource management, sustainability and security.
From May, new dives live from theOkeanos Explore are planned, with first a running-in mission in the deep waters off Hawaii. On April 30, 2026, biologist Allen Collins will also host a webinar devoted to the discoveries of the Seascape Alaska expeditions, including the history of this famous golden sphere.
