For much of history, the ocean was regarded as an inhospitable, inaccessible realm. Explorers
endeavoured to cross it, to discover new lands and expand empires. But while these pioneers
gazed out across the waves in search of a new world, few thought to look downwards.
Perhaps they thought it futile. After all, the mainstream scientific viewpoint was that
life could not exist more than 550 metres (1,800 feet) beneath the surface of the ocean.
An idea proposed by Edward Forbes in 1834 known as the Abyssus theory. He believed that
the abundance and variety of marine life decreased with increasing depth, and calculated that
it ceased to exist at a certain depth. But many challenged him, giving way to vastly
increased efforts in deep sea exploration, so much so that it led to the Royal Navy granting
use of a ship called the HMS Challenger, for a global expedition. A voyage that would help
lay the foundations of modern oceanography.
Portsmouth, England. The date is the 21st December 1872, and something remarkable is
taking place. The HMS Challenger is departing from the port, captained by George Nares.
Scottish natural historian and naturalist Charles Wyville Thompson occupies the role
of scientific supervisor. He has modified the ship for scientific task, equipping it
with laboratories, loading specimen jars with alcohol to preserve samples, microscopes,
trawls and dredges, sounding leads, devices to collect sediment from the deep sea, and
great lengths of rope to suspend the equipment into the depths. This expedition was to be
the first of its kind. One organised specifically to gather data on the ocean environment and
its inhabitants.
As a supporter of the then-recent theory of evolution, Thomson believed that the deep
sea would be home to missing links and living fossils. Creatures that were long extinct
in shallower regions. He believed that the conditions of extreme cold, intense darkness,
and a lack of currents, created an environment that was stable and unchanging, allowing evolution
to slow or stop completely. Many scientists expected him to find “representatives of
earlier geological periods”, and “zoological antiquities which in the tranquil and little
changed depths of the ocean have escaped the causes of destruction at work in the shallows
and represent the predominant population of a past age”.
This was somewhat supported, when a few organisms previously thought to be extinct were found
and catalogued among the countless newly discovered species.
A team of 5 scientists on board the HMS Challenger conducted the research, and over a 3 year
period at sea they studied the oceans at 360 stations around the world, measuring depth
and collecting samples. To measure the bottom depth, they lowered a line with a weight attached
to it until it reached the sea floor. A method called lead and line sounding.
On 23 March 1875, in the southwest Pacific Ocean between Guam and Palau at station number
225, the crew recorded a sounding of 4,475 fathoms. A depth that translates to 8,184
metres, or 26,850 feet, in the southern area of the Mariana Trench. The crew had not expected
to find a spot to be so deep; the first time they sent down a weight to measure the depth,
they ran out of rope. When they sent down a thermometer, the glass cracked. They had
discovered the deepest known place on the ocean floor, now estimated to be a few thousand
metres deeper than their initial measurements. The discovery of this location, now bearing
the name the Challenger Deep, led to a huge broadening in our understanding of oceanography.
In addition to the use of sounding, the crew would drag a weighted net with a 10-foot-wide
mouth across a patch of the ocean floor and haul aboard the sea creatures and sediments
it dredged up. Upon retrieving the nets at the surface, the crew sorted, rinsed and stored
specimens for examination upon return, preserving them in brine or alcohol.
A young assistant ship's steward, Joseph Matkin, wrote to his cousin, “When the dredge is
hauled up [the scientists] stand round in their shirt sleeves, and commence overhauling
the mud for fish etc., and as soon as they get any, down they all go to dissect and pickle
them in glass jars.”
Every time they dredged the bottom of the ocean, they would bring up weirder and weirder
creatures at deeper and deeper levels, as it quickly became apparent that the oceans
are teeming with life. And in March of 1875, after more than 2 years at sea, the crew of
the HMS Challenger made a remarkable discovery. Using a deep sea dredge, they uncovered an
abundance of life at depth well beyond 1,800 feet, disproving Forbes’ Abyssus theory
once and for all.
During its 127,580 km (79,280 mi) journey circumnavigating the globe, the crew on board
the Challenger took 492 deep sea soundings, and 284 dredges and trawls. This led to the
discovery of 4,700 new species of marine life, recorded in volumes and illustrated
by the official expedition artist, John James Wild.
One drawing shows the crew hauling aboard a large shark, while two of the ship’s dogs
look on warily.
But the hauls were not always so exciting. “The mud! Ye gods, imagine a cart full of
whitish mud, filled with minutest shells, poured all wet and sticky and slimy on to
some clean planks. In this the naturalists paddle and wade about, putting spadefuls in
successively finer and finer sieves, till nothing remains but the minute shells.”
Many of the specimens they found are now stored at the spirit collection of the Natural History
Museum in London.
The voyage saw the Challenger travel from England to the North Atlantic and the Caribbean,
down to Brazil and east to the southern tip of Africa. They dipped down within sight of Antarctic
icebergs and then headed up along Australia’s southeast coast, making their way through
Micronesia and Asia, then east across the Pacific, tracing South America and arriving
back in England on May 24, 1876, three and a half years after the journey’s start.
A wealth of information about the marine environment was yielded, all catalogued in the Report
of Scientific Results of the Exploring Voyage of H.M.S Challenger during the years 1873-76.
A publication that would be the greatest advance in the knowledge of our planet since the 16th
century. A wealth of data so vast that it filled 50 volumes with 30,000 pages of information,
marking a scientific revolution. Just 5 scientists during the course of 3 years managed to lay
the foundations of oceanography.
Much like our theories about the cosmic expanse of the universe, our ignorance meant we once
thought it unlikely that life could survive in the depths because of our knowledge of
pressure and the extreme conditions down there. But now, ocean science could advance in the
knowledge that the depths concealed yet more secrets. The Challenger Expedition’s exciting
discoveries encouraged other countries to take interest in the oceans and to mount their
own expeditions. In the years since, entire ecosystems have been found in the deep ocean.
Hydrothermal vents were discovered as recently as 1977, teeming with unique creatures relying
entirely on energy produced by the earth itself, rather than sunlight.
We have still only scratched the surface. There is no doubt that the future of ocean
exploration will hold many more incredible discoveries, with organisations like OceanX
and MBARI leading the way in developing the vital technology needed to get closer than
ever before to the other world beneath the waves.