With a name like the ‘Hot Tub of Despair’, you might not be surprised to learn that this bizarre structure is more dangerous than it might first appear.
While it may seem like a harmless pool of cloudy water to the naked eye, the Hot Tub of Despair is so deadly that almost anything that enters is instantly killed.
The 100ft (30.5m) wide ‘bottomless’ pond contains a toxic mix of ultra-salty water, methane, and hydrogen sulphide which only a handful of creatures can survive.
When it was discovered in 2015, researchers found that the banks were littered with the preserved corpses of creatures that had tried to swim in the warm waters.
And, to make things even stranger, this pool sits more than 1,000m (3,300ft) beneath the waves of the Gulf of Mexico.
This pool contains a mixture of highly salty brine which is toxic to any creature that is unfortunate enough to fall in. Note the dead crab in the pool
In 2015 researchers discovered a site nicknamed the ‘Hot Tub of Despair’ 1,000m (3,300ft) beneath the waves of the Gulf of Mexico
The Hot Tub of Despair was discovered by the Ocean Exploration Trust as part of an investigation into ‘cold seeps’ in the depths of the Gulf of Mexico.
These are regions where dense hydrocarbons, the basis of oil and petrol, are pushed out from beneath the seafloor and into the water column.
Cold seeps form over vast layers of salt created when ancient oceans evaporated.
As these salt layers shift and crack, the resulting gaps allow compounds normally trapped beneath the ground to escape.
Sometimes, when these cracks form, water deep in the sediment layers dissolves huge amounts of salt to form a brine four times saltier than seawater.
The researchers found the bodies of several crabs which had been ‘pickled’ by the brine for so long that mineral deposits were beginning to form on their bodies (pictured)
Since this brine is so dense, it sits at the bottom of the ocean and cannot easily mix with the surrounding salt water.
In places where the saltwater wells up from the ground, ‘brine pools’ can form strange underwater lakes and ponds such as the Hot Tub of Despair.
While piloting a remote-operated vehicle, named Hercules, the researchers found a steep thin wall – mainly made of deposited minerals and live mussels – rising three meters above the seafloor.
They found that this contained a 12ft (3.7m) deep layer of brine above a ‘bottomless’ pool of liquidised mud.
Even after extending a sampling line more than 60ft (19m) into the pool, the researchers could never find the bottom.
The salty water within is far hotter than the surrounding area, reaching 19°C (66°F), and is deadly to any large creatures who happen to enter – giving the pool its ominous nickname.
Although the brine itself is 12ft (3.7m) deep, when the remote-operated vehicle inserted a probe (pictured) they could not find the bottom of the liquidised mud layer even after 60ft (19m)
The researchers spotted the bodies of several crabs and arthropods which had been ‘pickled’ by the salty water.
Due to the intense salinity, and high levels of methane and hydrogen sulphide from the bubbling hydrocarbons, entering the brine pool is usually fatal.
In a video of the expedition shared by Nautilus Live, one of the researchers says: ‘These types of larger organisms really don’t like to be in this fluid.’
In one case, the researchers spotted the body of a large crab on top of an arthropod, both dead in the brine.
They suggested that the crab may have seen the body of the arthropod in the pool and followed it in the hopes of an easy meal.
In the absence of any oxygen, the bacteria which normally break down bodies simply cannot survive.
The pool formed where layers of salt formed by the evaporation of ancient oceans shift and crack, allowing hydrocarbons and salty water to well up from below
Some of the corpses had been in the water so long that they had been coated with a layer of mineral deposits including large halite crystals.
The researcher added: ‘Maybe they just come here to die. They’re preserved in perpetuity, they basically get embalmed here.’
However, despite how deadly the Hot Tub of Despair may be to most creatures, some forms of life have been able to flourish.
In fact, the researchers believe that living creatures may have been partly responsible for helping the pool to form.
One researcher said in the video: ‘Initially, probably what happens is fluid starts to erupt from the seafloor, and then you get biological communities that start taking advantage of that.’
In the wall of the brine pool, the expedition team found two species of mussels that appeared to be playing a key role in keeping the wall intact.
The wall of the pool is being held together by a colony of mussels which thrive in the toxic waters
These mussels (pictured) contain bacteria in their gills which are able to convert the dissolved gasses into energy for their hosts and support an active ecosystem with many different species
As the researchers note in a summary of the expedition’s findings, these mussels contain symbiotic bacteria in their gills which convert dissolved gasses into energy for their hosts.
These bacteria support a small but complex ecosystem of mussels, worms, corals, and small animals in and around the deadly brine.
In one video captured by the expedition team, the researchers even watched as a fish repeatedly dived into the brine pool and swam into the edges.
It was theorised that this fish could have a tolerance to the brine and is diving in the pool to feed – although the researchers note it could have just been sick.
The ecosystems that surround these strange, hostile regions of the planet are vital to our scientific understanding of life.
By seeing how lifeforms can adapt and thrive in the most extreme conditions, scientists may one day shed light on the origins of life on Earth and on how life may form on distant planets.
