The man who discovered life without sunlight
Dr Robert Ballard is best known for locating the wreck of the Titanic, but he values more highly the discovery made on an expedition to the Galapagos Rift in 1977.
The expedition, which was originally tasked with finding hot springs at the bottom of the ocean, stumbled across 'exotic' life forms existing in total darkness, that survive on the chemical energy in hydrogen sulphide released from the bowels of the earth.
Dr Ballard says their discover has transformed our understanding of life not only on earth, but throughout the universe.
18 Jul 2014