The Eltanin Antenna
DebunkedSummary
In 1964 an American research vessel lowered a camera nearly four kilometres to the floor of the southeast Pacific and photographed something standing on the sediment. It has a central mast. It has whorls of evenly spaced arms radiating from it at intervals. It looks exactly like a television aerial.
It became a fixture of the UFO literature for forty years.
It is a sponge. It was described, drawn, and named by a scientist in 1888, seventy-six years before the photograph was taken, and the description was sitting in the literature the entire time.
What is documented
The photograph. On 29 August 1964, the USNS Eltanin, a United States Antarctic research vessel, photographed the seafloor at a depth of approximately 3,900 metres, west of Cape Horn.
The image shows a slender vertical structure rising from the sediment, with sets of arms projecting from it at regular intervals up its length, each set arranged symmetrically around the stalk. The arms end in small terminal knobs.
Why it looks artificial. Because it is symmetrical, evenly spaced, and repeated. Those are the properties people associate with manufacture, and they are also, as it happens, extremely common in biology.
The claim. From the 1960s onward the image circulated as evidence of an alien or otherwise artificial object on the deep seafloor. It appeared in books, in television programmes, and eventually across the internet.
The identification. In 2003, Tom DeMary identified the object as Chondrocladia concrescens: a carnivorous deep-sea sponge.
The 1888 description. Chondrocladia concrescens was described by Alexander Agassiz in 1888. His account describes a long stem terminating in a bunch of root-like structures, with the stem carrying nodes bearing several club-shaped appendages, and notes that they cover the seafloor like a thicket.
That is the object in the photograph. The description predates it by seventy-six years.
Leading explanations
It is Chondrocladia concrescens. Settled.
The sponge anchors itself in soft sediment by a root system, sends up a stalk, and carries whorls of club-tipped appendages along it. The regularity that made the object look manufactured is the ordinary radial symmetry of a sessile organism, which is very common and which has nothing to do with anybody having made anything.
Why nobody noticed for forty years. They did notice. Marine biologists who saw the image recognised what it was, because they were familiar with the genus and it looked like the genus.
What did not happen is that anybody publishing the image as an alien artefact ever asked one. The identification required opening a paper from 1888 and looking at a drawing, and for four decades nobody who was making the claim did that.
What the popular version gets wrong
"It cannot be natural, it is too symmetrical." Radial symmetry is one of the most common structural plans in the animal kingdom. A sea anemone is more symmetrical than most things a person has ever built. Symmetry is not a signature of manufacture, and the intuition that it is has produced more bad conclusions in this archive than any other single assumption.
"It was never explained." It was described in 1888, which is to say it was explained before it was photographed. The interval between the taking of the picture and the pointing-out of the answer is not the time it took to solve the case. It is the time it took for somebody to look.
"The photograph was suppressed." It was published by the research programme that took it. It was available. The claim survived not because the evidence was hidden but because the answer was in a place that nobody making the claim was willing to go, which was a nineteenth-century sponge monograph.
Current status
Debunked. A carnivorous sponge, standing on the seafloor, doing what its species has done for a very long time.
The registry keeps this record because of the shape of the failure, which is the same shape as several others in this archive. The answer was not missing. It was not classified, or lost, or destroyed. It was published, in a journal, in 1888, with a picture.
It took thirty-nine years, from the first serious circulation of the claim, for anybody to go and read it.
Sources
- USNS Eltanin, seafloor photograph, 29 August 1964, at approximately 3,900 m depth.
- Agassiz, A. (1888). Description of Chondrocladia concrescens.
- DeMary, T. (2003). Identification of the photographed object as Chondrocladia concrescens.
- Subsequent literature on carnivorous sponges of the genus Chondrocladia.
Last reviewed: July 2026. Records are provisional. Where the evidence changes, the entry changes. Found an error? Tell us.