The deepest underwater hydrothermal vents ever known have been discovered by a robot exploring waters off the Cayman Islands in the Caribbean.

The black smokers, as these vents are known, are 5 kilometres down in the Cayman Trough, half a mile deeper than previously found deep vents, and were discovered by scientists working on the Royal Research Ship James Cook, led by Doug Connelly of the National Oceanography Centre in Southampton.

The robot showed spires protruding from the seafloor, made of copper and iron ores. These spires were spurting out super-heated water, hot enough to melt lead according to the expedition blog and press release.

“It was like wandering across the surface of another world,” says geologist Bramley Murton from the UK National Oceanography Centre in Southampton, who piloted the HyBIS underwater vehicle. “The rainbow hues of the mineral spires and the fluorescent blues of the microbial mats covering them were like nothing I had ever seen before.”

Hydrothermal vents harbour weird life, amazingly adapted to surviving the inhospitable, extreme environment that supports them. Next step is to compare the living things in these vents to those that exist in other deep sea vents around the world.

Coverage elsewhere: BBC, Daily Mail, Fox, AP.