A puzzling picture from the seabed
On August 29, 1964, the USNS Eltanin, the world's first dedicated Antarctic research vessel, was surveying the seabed west of Cape Horn. From a depth of 3,904 meters (12,808 feet), its deep-sea camera captured a startling image. Jutting from the abyssal mud was a perfectly vertical stalk with a series of cross-bars, each ending in a small sphere. The object appeared symmetrical and rigid. The first public report of the photograph appeared in the New Zealand Herald on December 5, 1964, under the headline "Puzzle Picture From Sea Bed".
The ship that made the discovery, the USNS Eltanin, was an ice-breaking cargo ship converted into a floating laboratory in 1962. Between 1962 and 1972, it conducted 52 research cruises, surveying about 80% of the Southern Ocean. The data it collected on magnetic profiles of the seafloor provided important evidence for the theory of continental drift by confirming sea floor spreading. The photograph of the strange "antenna," however, would launch a mystery of a very different kind.
Theories and a biological reality
The image's seemingly technological nature fueled decades of speculation. In 1968, author Brad Steiger described it as an "astonishing piece of machinery" resembling a mix of a TV and telemetry antenna. The most persistent theory came from a New Zealand airline pilot and author, Bruce Cathie, who argued in his 1968 book Harmonic 33 that the object was an alien navigation beacon, part of a global energy grid used by UFOs. For years, the "Eltanin Antenna" was a celebrated out-of-place-artifact in UFO and paranormal literature.
The scientific explanation is less sensational. In 1971, oceanographers Bruce C. Heezen and Charles D. Hollister identified the object in their book The Face of the Deep. It was a carnivorous sponge, Chondrocladia concrescens (a species first described in 1888, previously known as Cladorhiza concrescens). Sponges in the Cladorhizidae family are deep-sea predators. Lacking the filter-feeding systems of other sponges, they use elaborate, symmetrical structures to capture small crustaceans and other prey drifting in the abyssal currents. The "antenna" is an efficient feeding apparatus, with the spheres at the tips of its branches likely covered in tiny, hook-like spicules to ensnare food.