By David Shukman / BBC News
The future of electric cars may depend on mining critically important metals on the ocean floor.
That's the view of the engineer leading a major European investigation into new sources of key elements. Demand is soaring for the metal cobalt - an essential ingredient in batteries and abundant in rocks on the seabed. Laurens de Jonge, who's running the EU project, says the transition to electric cars means "we need those resources".
Apollo II is a prototype deep sea mining machine being tested off the coast of Malaga.
He was speaking during a unique set of underwater experiments designed to assess the impact of extracting rocks from the ocean floor.
In calm waters 15km off the coast of Malaga in southern Spain, a prototype mining machine was lowered to the seabed and 'driven' by remote control.
Cameras attached to the Apollo II machine recorded its progress and, crucially, monitored how the aluminium tracks stirred up clouds of sand and silt as they advanced.