The Mariana Trench is one of the most mysterious places on Earth.
The trench is over eleven kilometers (36,201 feet) deep and lies on the floor of the Pacific Ocean. It is so difficult to reach that only a handful of people have ever descended it.
It is therefore no surprise that the unusual sounds coming from the Mariana Trench, when first recorded in 2014, sparked fears of an alien invasion.
The sounds lasted 2.5 to 3.5 seconds and were called ‘biotwangs’, but their source was unknown.
Ten years later, scientists from the National Oceanic and Atmospheric Administration (NOAA) have reanalyzed the sounds and believe they have finally revealed the truth.
The Mariana Trench (artist’s impression) is one of the most mysterious places on Earth
The strange sounds were first recorded in 2014 by underwater gliders used to conduct acoustic surveys in the trench.
The five-part sounds last between 2.5 and 3.5 seconds and consist of deep groans with frequencies up to 38 hertz and a metallic finale that reaches up to 8,000 hertz.
Researchers were initially baffled by the sounds.
However, in 2016, a team from Oregon State University (OSU) suggested that it may have been a new type of baleen whale call that had not been heard before.
Sharon Nieukirk, a senior research assistant in marine bioacoustics at Oregon State University, said at the time: “It’s quite extraordinary, with all these crazy parts.
‘The low-frequency groan is typical of baleen whales, and it’s that nasal sound that makes it truly unique.
“We don’t find many new sounds from baleen whales.”
Now, scientists have reanalyzed the sounds using a combination of visual and acoustic survey data. Their findings suggest the OSU team wasn’t far off the mark.
The Mariana Trench is nearly seven miles (36,201 feet) deep and lies on the bottom of the Pacific Ocean. It is so difficult to reach that only a handful of people have ever ventured there.
The eerie sounds were first recorded in 2014 by underwater gliders used to conduct acoustic surveys of the trench. The five-part sounds last between 2.5 and 3.5 seconds and include deep groans at frequencies as low as 38 hertz and a metallic finale that soared to 8,000 hertz
The new research shows that Bryde’s whales are not responsible for the jellyfish, but rather baleen whales.
Writing in their study, published in Frontiers in Marine Sciencethe team led by Dr Ann Allen explained: ‘It was assumed to have been produced by a baleen whale, but without visual verification it was impossible to assign a species.
‘Using a combination of visual and acoustic survey data collected in the Mariana Archipelago, we determined that Biotwangs are produced by Bryde’s whales.’
Bryde’s whales are found worldwide in warm, temperate oceans, including the Atlantic, Indian and Pacific oceans.
Bryde’s whales are found throughout the world in warm, temperate oceans, including the Atlantic, Indian and Pacific oceans.
The Mariana Trench is nearly seven miles (36,201 feet) deep and lies on the bottom of the Pacific Ocean. It is so difficult to reach that only a handful of people have ever ventured there.
The researchers saw 10 whales swimming in the area and even recorded nine of them making the characteristic sounds.
To prove that the whales were indeed the source, the team used artificial intelligence.
“We used a combination of manual and machine learning annotation methods to detect Biotwangs in our extensive historical passive acoustic monitoring datasets collected in the central and western North Pacific,” they explain in the study.
‘We have observed a consistent seasonal presence of Biotwangs in the Mariana Archipelago and east of Wake Island, with occasional sightings as far north as the Hawaiian Islands and near the equator (Howland Island).’
The team still doesn’t know why the whales’ calls are so unusual, or why they are being called at all.
However, if you with Popular scienceDr. Allen suggested, ‘It’s possible they use the biotwang as a contact call, a sort of “Marco Polo” of the ocean.
“But we need more information before we can say that for sure.”