Mysterious giant beasts may lurk in the darkest depths of the ocean making whale-like noises that are baffling scientists.
Researchers have nicknamed the strange unidentified sound picked up by undersea microphones ”Bloop”. While it bears the varying frequency hallmark of marine animals, it is far more powerful than the calls made by any creature known on Earth.
In 1997, Bloop was detected by sensors up to 4828 kilometres apart, New Scientist magazine reported. That meant it had to be much louder than any recognised animal noise, including that produced by the largest whales.
One suggestion is that the sound is coming from giant squid, which live at extreme depths of up to four kilometres.
Although dead giant squid have been washed up on beaches, and telltale sucker marks have been seen on whales, there has never been a confirmed sighting of one of the elusive cephalopods in the wild.
The largest dead squid on record measured over 18 metres including the length of its tentacles, but no-one knows how big the creatures might grow. However Phil Lobel, a marine biologist at Boston University in Massachusetts, US, doubts that giant squid are the source of Bloop.
”Cephalopods have no gas-filled sac, so they have no way to make that type of noise,” he said. ”Though you can never rule anything out completely, I doubt it.”
Nevertheless he agrees that the sound is most likely to be biological in origin. The system picking up Bloop and other strange noises from the deep is a military relic of the Cold War. In the 1960s the US Navy set up an array of underwater microphones, or hydrophones, around the globe to track Soviet submarines.
The listening stations are hundreds of yards below the ocean surface at a depth where sound waves become trapped in a layer of water known as the deep sound channel. Here temperature and pressure cause sound waves to keep travelling without being scattered by the ocean surface or bottom.
Most of the sounds detected emanate from whales, ships or earthquakes, but some very low frequency noises have proved puzzling. Scientists believe many of these – given names such as Train, Whistle, Slowdown and Upsweep – can be explained by ocean currents, volcanic activity, or the movement of Antarctic ice.
But Bloop remains a tantalising mystery. – Sapa-DPA