Scientists have solved the mystery of the “golden orb,” a strange deep-sea object collected during a 2023 government expedition that sparked two-plus years of public curiosity and scientific debate.

The National Oceanic and Atmospheric Administration announced Wednesday that the golden mass — discovered more than two miles down in the Gulf of Alaska — is a remnant of dead cells from the base of a giant deep-sea anemone, Relicanthus daphneae, specifically the portion that had anchored the creature to the seafloor.

The object was found in 2023 during NOAA’s Seascape Alaska 5 expedition, when the remotely operated vehicle Deep Discoverer, deployed from NOAA Ship Okeanos Explorer, encountered the mound-shaped, golden object adhered to a rock at a depth of 3,250 meters. Scientists were immediately stumped. Was it an egg case? A dead sponge? Something that had crawled in — or out?

The at-sea team collected the orb using a suction sampler and sent it to the Smithsonian National Museum of Natural History for examination. What followed was a lengthy, multi-disciplinary investigation.

“We work on hundreds of different samples and I suspected that our routine processes would clarify the mystery,” said Allen Collins, a zoologist and director of NOAA Fisheries’ National Systematics Laboratory. “But this turned into a special case that required focused efforts and expertise of several different individuals. This was a complex mystery that required morphological, genetic, deep-sea and bioinformatics expertise to solve.”

Scientists with NOAA Fisheries and the Smithsonian used an integrative taxonomic approach, combining physical structural analysis with genetic testing. Initial examination found the object lacked typical animal anatomy but was fibrous and packed with cnidocytes — stinging cells characteristic of cnidarians such as corals and anemones. Smithsonian researcher Abigail Reft identified the cells more specifically as spirocysts, a type found only in the Hexacorallia subclass of cnidarians.

Early DNA barcoding proved inconclusive, likely due to contamination from microscopic organisms living on the specimen. Researchers then turned to whole-genome sequencing, which confirmed animal DNA and a strong genetic signal from a giant deep-sea anemone. Sequencing the mitochondrial genomes of the golden orb and a similar specimen collected in 2021 during a Schmidt Ocean Institute expedition confirmed both were nearly genetically identical to a known R. daphneae reference genome.

The full anemone, rarely observed because of the extreme depth at which it lives, has long tentacles and can grow to roughly three feet across. Scientists determined the golden orb was the animal’s cuticle, a basal structure usually hidden beneath the anemone and left behind when the creature moves or undergoes a form of asexual reproduction.

“So often in deep ocean exploration, we find these captivating mysteries, like the ’golden orb,’” said Capt. William Mowitt, acting director of NOAA Ocean Exploration. “With advanced techniques like DNA sequencing, we are able to solve more and more of them.”