Alien-like creatures dwell among us. Even as we shoot people into space to research un­known life forms, we have a blind spot right in front of our noses: the deep ocean, home to living organisms with bizarre survival strat­egies and strange, disquieting appearances. A global network community of researchers is working on building a taxonomy of this un­known realm—and is in a human-caused race against time.

Essay by Tanja Pabelick

One March day in the year 2005, a submersible called Alvin glides over the sea bed south of the Easter Islands, its depth gauge showing 2200 metres below sea level. The beam of its powerful lamp skims over rocks, sand and hydrothermal vents, the small spotlight the only point of brightness amid the unrelieved darkness. The scientists controlling Alvin are two kilometres further up, on board the expedition vessel Atlantis. The oceanographers and engineers are here because of the tectonic plates that shift and slip along precisely this band of coordinates to create a unique phenomenon: black smokers, These are underwater vents that belch heated water rich in sulphides into the surrounding seawater, which has a temperature of just two degrees; the warmer borders of these emissions are transformed into a densely populated oasis. Life here starts with bacteria which convert the inorganic substances into organic compounds and form the first link in a food chain that takes in shrimps, bivalves and starfish as it progresses. The researchers’ goal is to discover how the organisms travel through the cold, hostile darkness from one vent to the next. Suddenly, something fuzzy whisks past the camera lens. The scientists frantically manoeuvre Alvin’s camera to track the creature, and finally succeed in capturing the ocean denizen using the submersible’s remote-controlled instruments. The fifteen-centimetre creature that lands on deck is something none of them have ever seen, let alone held, before. It’s a crab, but an eyeless crab with legs covered with long pale yellow fur and claws coated in bacterial growth. This crab is not only a new species; it’s part of a previously unknown family. It is soon christened with a name probably inspired by its retiring nature and furry coat: the yeti crab.

While the specimen discovered by Alvin is later carefully preserved in a jar and ends up in the French Muséum national d’Histoire, the scientists’ video of the bizarre creature goes viral. Kiwa hirsuta, or hairy crab, sweeps the Japanese market as a soft toy, stars in comic strips, and is even recreated as a LEGO model. The yeti crab becomes an icon of pop culture. In fact, however, it is only one of a gang of oddities, ocean-dwelling superheroes each with its own individual talent. Take the barreleye, which can keep a lookout for enemies stalking it from above by swivelling its eyes in its transparent head; or the anglerfish, whose luminescent fin acts as a lantern to lure in its prey; or the black swallower, which can distend its stomach to accommodate fish three times larger than itself. Many of these bizarre creatures can be found in clips on YouTube and profiles in the Census of Marine Life, a database documenting ocean life. But most of them have never encountered a human. That’s because all the time we are striving to prove the existence of water on Mars, we already have a pretty alien planet right here on our own earth, with inhabitants that outdo most alien fiction in strangeness.

The oceans cover around 70 per cent of the earth’s surface and have an average depth of around 4000 metres, with the exception of some oceanic trenches such as the Mariana Trench, which may be as much as eleven kilometres deep. Darkness falls quickly; from a depth of 200 metres there is little discernible light, and from 800 metres the water is pitch-black. Deep oceans are no place for humans. Pressure increases by the equivalent of one atmosphere with every ten metres of descent, and in the darkest depths it is 100 to 1000 times higher than normal air. Free divers have descended up to 110 metres, while the overall record for diving, held by an Egyptian scuba diver, is around 330 metres. Submersibles can plunge to 1000 metres. Yet these deep oceans account for around 78 per cent of our planet’s biosphere, rising to 99.5 per cent when oceans as a whole are considered. That remaining half per cent is the land biosphere—our habitat. And while we are familiar with virtually every inch of the jungles or mountains on land, vast swathes of the deep oceans have never been visited by humans. It’s pure chance that the yeti crab made it all the way from the sea bed to a toy shelf in Japan. We only know what it looks like because Alvin the submersible snapped it up and brought it to the surface. However, its existence had already been known for some years; in 2001, the creature encountered another submersible belonging to the German research vessel Sonne, but at the time the furry crab was not captured and described and was thus never officially documented.