ONE of only three rare submarines in the world vanished during an underwater hunt at the "Doomsday Glacier" in Antarctica.
The 23-ft vehicle, worth £3million, was exploring the treacherous icy terrain when it disappeared without a trace.
Ran, the autonomous underwater vehicle (AUV), is equipped with high tech sensors and features that allow it to remain underwater for long stretches of time.
On only its second trip to the icy destination, Ran vanished last weekend and one of the scientists monitoring it said "something prevented it from getting out".
It's first trip there had been a successful one in 2019 - when scientists became the world's first researchers to dive under the formidable glacier thanks to the high tech device.
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They sent the sub underwater to get incredible close-up images and data about what was happening underneath the surface.
By staying in intermittent contact with a ship above the ice, Ran is programmed to follow a certain journey under the water before returning safely to it's prearranged meeting spot.
But this time around - the drone sub didn't resurface when it was supposed to.
Anna Wahlin, an oceanography expert and a member of the Ran research team, said: "It's a bit like looking for a needle in a haystack, but without even knowing where the haystack is.
"At this point, Ran's batteries are dead. All we know is that something unexpected happened under the ice.
"We suspect it ran into trouble, and then something prevented it from getting out."
The research team working over there are not hopeful that they will recover the kit, which could be anywhere under the vast sheet of ice.
Their website explains that the sub only has a battery life of 36 hours.
Ran can dive underneath ice which measures between 650 and 1,640 feet thick.
It's a vital piece of tech for scientists hoping to study the brutal and remote conditions - and rising sea levels.
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The Doomsday Glacier is so thick that if it melted and collapsed the global sea level could rise by more than two feet.
And the Thwaites glacier is the widest one on Earth, stretching over 74,000 square miles.
It's even bigger than Florida - and has earned its formidable name through its potentially colossal impact on sea levels around the world if the ice continues to melt.
Scientists have been trying to study it for years to learn more about how and why the ice is melting, and what the implications of that are.
Wahlin, who works at the Swedish University of Gothenburg that funds the sub, said: "This was the second time we took Ran to Thwaites Glacier to document the area under the ice.
"Thanks to Ran, we became the first researchers in the world to enter Thwaites in 2019, and during the current expedition we have visited the same area again.
"Even if you see melting and movements in the ice from satellite data, from Ran we get close-ups of the underside of the ice and information about exactly which mechanisms are behind the melting."
She described the disappearance of Ran as a "very big loss".
The high-tech sub, which weighs over 4,000 pounds, is kitted out with sensors to detect temperature and death, oxygen and levels of carbon dioxide.
It has sonars to scan around the sides and below and uses satellite, radio and WiFi to communicate with people on the ground.
While a small recovery system is stationed nearby, a larger one was in production when Ran vanished.
It moves faster than an ROV, a remotely operated vehicle, and can cover longer distances in a shorter time.
Sadly the impressive device had completed several successful dives earlier on in January before it vanished.
It's main ship, helicopters and drones all searched the glacier, but were unable to find it.
Wahlin added: "Personally, I'm of the opinion that this is a better end than having the AUV aging gathering dust in a garage.
"At the same time, it is of course a very big loss."
