Into the deep

A new type of robotic vehicle called Nereus has successfully reached the deepest part of the world’s ocean.

Nereus dived to 10,902m (6.8 miles) in the Mariana Trench in the western Pacific Ocean on 31 May, making it the world’s deepest-diving vehicle.

The unmanned vehicle itself was remotely operated by pilots aboard the surface ship Kilo Moana via a lightweight, thin, fibre-optic tether that allowed it to reach the record depth.

The Nereus engineering team, led by Andy Bowen from the Woods Hole Oceanographic Institute, knew that, to reach this depth, a tethered robot using traditional technologies would be prohibitively expensive to build and operate. So they used innovative methods to strike a balance between size, weight, materials cost and functionality.

The tethering system presented one of the greatest design challenges. Traditional robotic systems use a steel-reinforced cable containing copper wires to power the vehicle and optical fibres to enable information to be passed between the ship and the vehicle. But if such a cable had been used to reach the seafloor in the Mariana Trench, it would have snapped under its own weight.