JUST off the coast of the world’s driest desert, the lifeless Atacama in northern Chile, lies one of the largest and densest masses of life anywhere on Earth. The vast tangled mat of white “hair”, which has an area of 128,000 square kilometres, roughly the size of Greece, was recently mapped as part of the first comprehensive Census of Marine Life.

The ghostly submarine prairie is made of wispy strings of giant bacteria, says Victor Gallardo, a marine biologist at Chile’s University of Concepción. The bug thrives in water almost devoid of oxygen by extracting energy from hydrogen sulphide …