In 1977, the year the movie Star Wars: Episode IV – A New Hope was released, marine geologists laid eyes on a deep-sea hydrothermal vent for the first time.
They were diving inside the submersible, known as Alvin, in the eastern Pacific Ocean at a depth of around 2,500m (8,200ft).
Peering through Alvin’s small porthole, the scientists were gobsmacked to see the tall, rocky chimneys were not only belching out scorching hot fluids, but also that they were absolutely covered in animals.
This oasis of life was just as strange as anything George Lucas created.
Pompeii worms (Alvinella pompejana) were one of the species found in the first wave of hydrothermal vent explorations during the late 1970s and early 1980s.
These pink worms grow to around 15cm (almost 6in) and are covered in grey fuzz. At their head end is a cluster of red gills that make them look a bit like a Demogorgon monster from the Netflix series Stranger Things.
Scientists named these strange worms jointly after the submersible Alvin and the ancient Roman city that was famously destroyed by a volcano.
While Pompeii worms don’t actually live on active volcanoes, their homes are hardly any more hospitable.
Hydrothermal vents are the deep sea’s version of thermal springs, except much hotter and more toxic than anything on land.
They form at the edges of the ocean’s tectonic plates, where shallow magma chambers heat seawater as it seeps through porous seafloor rocks, then gushes back up at several hundred degrees Celsius.
No wonder Pompeii worms have earned a reputation as one of the most heat-proof animal species. Probes inserted into the thin tubes they build on the sides of vent chimneys have registered temperatures between 60–80°C (140–176°F) at the tail end.
Temperature spikes of over 100°C (212°F) don’t seem to bother the worms either. Scientists don’t yet fully understand how Pompeii worms can handle this heat, but their grey fuzzy coats may be insulating them from the worst of it.
The coats are made of bacteria, which the worms feed with mucus – suggesting this is a deliberate living arrangement and not just a chance thing. The bacteria seem to help circulate cooler seawater around the worm’s body. They likely also detoxify heavy metals that pour out of hydrothermal vents.
More of the Pompeii worms’ secrets lie in their genes. They produce a super-tough version of a heat-shock protein that stops vital molecules from breaking down in the heat. They also produce a form of collagen that withstands extreme pressure, so their bodies don’t collapse.
These remarkable worms may also have a very science-fiction way of colonising the deep sea. In a laboratory, scientists have cooled their eggs to 2°C (36°F), around the ambient temperature of the deep sea, away from hydrothermal vents.
The cooled eggs stopped dividing, but they didn’t die. When the water temperature was raised after a few days, the eggs continued developing.
This raises the possibility that Pompeii worms release their eggs to drift through the deep sea in a state of suspended animation. When they reach another hydrothermal vent, they wake up and begin a new colony.
Perhaps one day we’ll learn their secrets and use them to send humans to colonise other planets.
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