The ocean covers 71% of the surface of the earth and affects every aspect of human life from the food we eat to the air we breathe. Over half of the surface of the earth is covered by water more than 1000 m deep - it is often said we know more about the surface of the moon than we do about the deep ocean floor.
We began to learn about life in the deep ocean in the 19th century. Around this time Edward Forbes at the University of Edinburgh in Scotland suggested that the seabed below 600 m was lifeless. This idea stimulated others - could it really be true that no life existed over huge areas of the planet?
Around this time others were exploring the deep-sea, often in search of new sea passages or to survey the route for submarine cables. These deep-sea pioneers sometimes found animals caught on the sounding lines they used to measure water depth. In Norway Michael Sars and his son G.O. Sars found almost 100 species living below 600 m - including a live stalked sea lily that was only was only known from fossils.
In the UK, Charles Wyville Thomson became fascinated by the question of whether life could exist in the chilly waters of the deep-sea and whether the deep-sea was a refuge for species thought to be extinct. He visited Michael Sars in Norway and saw the animals dredged from deep in the fjords. On his return to Britain, Wyville Thomson and W.B. Carpenter organised an expedition with the Royal Society of London and using ships from the British Royal Navy (H.M.S. Lightning and H.M.S. Porcupine) set out in the summers of 1868-1870. These early cruises dredged down to over 4000 m - a fantastic achievement at the time.
Now convinced that life was present at the greatest ocean depths, Wyville Thomson organised the world-famous Challenger expedition using the H.M.S Challenger to circumnavigate the world between 1872 and 1876. As well as finding animal life at over 5000 m depth, this expedition examined the temperatures and salinities of the ocean and laid the foundations for the science of oceanography.