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The Challenger Expedition

The Challenger Expedition Worksheet

The first oceanographic expedition

Photo of Sir Wyville Thomson
John Murray
Photo of Sir Wyville Thomson
C. W. Thompson

The Challenger Expedition claims the title of the world's first totally scientific oceanographic expedition. By the time the HMS Challenger left the dock on December 21, 1872, the world was experiencing an intellectual and technological revolution of sorts. Except for the poles, few places remained to be conquered by man. And in a time when knowledge began to be equated with power, the British government was amenable to schemes for acquiring knowledge.

With a rising tide of intellectual fervor behind him, Sir Charles Wyville Thomson, a natural history professor at the University of Edinburgh in Scotland, and his Canadian-born student, John Murray (later, Sir John Murray) hatched a scheme to explore the oceans in the grandest oceanographic mission ever conceived. They called their proposal "oceanography" and pleaded their case before the Royal Navy and the Royal Society to send a ship around the world for one purpose: to study the oceans.

With the agreement that a portion of any profits from the trip would go to the government, Thomson and Murray secured a ship from the Royal Navy. The Challenger Society for Marine Science provides this best description of the HMS Challenger:

The vessel was a three-masted square-rigged wooden ship of 2300 tons displacement and some 200 feet [226 feet] overall. She was essentially a sailing ship though possessing an engine of 1200 horsepower. It was planned that the ship would be under sail for most of the cruise, using the engine primarily for maneuvering when conducting scientific observations and deploying heavy gear. All but two of the ship's 17 guns had been removed to make way for purpose-built scientific laboratories and workrooms designed specifically for biological, chemical and physical work. Storage space for all the trawls and dredges was also necessary, together with space for the anticipated sample collection.

HMS Challenger

H.M.S. Challenger was originally a British Royal Navy corvette, that is a small warship. It was first launched on 13 February 1858. It was a steam-assisted sailing ship. It was first assigned as part of the North America and West Indies fleet. In 1862, the Challenger took part in the French invasion of Mexico. France, Britain, and Spain were initially trying to get the Mexican government, under Benito Juarez, to pay its debts to them. When the British and Spanish realized France intended to conquer Mexico, they left in April 1862. Between 1866 and 1870, Challenger was assigned to the British fleet in Australia. In 1872, most of Challenger's cannons were removed, and the ship became the world's first totally scientific ocean research vessel.

The expedition's mission, by and large, was quite simple: to gather detailed and consistent observations of various oceanographic phenomena across as much of the ocean as possible. The sampling plan devised by Thomson and Murray resembles the sampling plan of modern day oceanographic expeditions; an assortment of physical, chemical, geological and biological measurements stretched over the day(s) at regular intervals across the sea. Samples that weren't analyzed on board were stored for laboratory analysis at the end of the expedition, a task that required the labors of more than 100 scientists.

Over the course of their voyage, the ship "stopped" and collected data and samples at 362 stations "at intervals as nearly uniform as possible". This systematic sampling plan belies one of the fundamental limitations of oceanographic research: gathering data over huge expanses that is representative of the ocean as a whole. Apparently, Thomson and Murray felt that an orderly sampling regime was best suited for their purposes. Whether they appreciated the complexity of the ocean environment and the difficulty of obtaining representative samples, I don't know. Their journals may shed light on this.

Nonetheless, here is the regimen they performed as best as possible at each of the 362 stations they visited:

  • The exact depth was determined.
  • A sample of the bottom averaging from 1 ounce to 1 pound in weight was recovered by means of the sounding instrument.
  • A sample of bottom water was procured for chemical/physical examination.
  • The bottom temperature was recorded by a registering thermometer.
  • At most stations, a fair sample of the bottom fauna (animals) was procured by means of the dredge or trawl.
  • At most stations, the fauna of the surface and of intermediate depths was examined by the use of tow nets variously adjusted.
  • At most stations, a series of temperature observations was made at different depths from the surface to the bottom.
  • At many stations, samples of sea-water were obtained from different depths.
  • In all cases, atmospheric and other meteorological conditions were carefully observed and noted.
  • The direction and rate of the surface current was determined.
  • At a few stations, an attempt was made to ascertain the direction and rate of movement of the water at different depths.
Buchanan Water Sampler
Buchanan Water Sampler
Challenger equipment
Sounding and Dredging
Apparatus

The equipment available to them for performing these measurements was typical for the times and, in some cases, not much different than what modern day oceanographers use. Water samples were procured using a device called a Buchanan water sampler, invented (apparently) by the chemist on the expedition, John Buchanan, a rather disagreeable fellow (according to reports). Like modern day water sampling devices, the Buchanan sampler was attached to a line in an open position and triggered with a metal (usually brass) messenger that tripped the sampling bottle closed. The sampler could then be hauled on board where portions of the water could be analyzed for temperature (and perhaps other shipboard analyses) or preserved for laboratory analyses.

Biological samples were obtained in a similar fashion: tying a device to a wire and towing it through the water or along the bottom. One of the many remarkable achievements of the Challenger Expedition was their discovery of marine organisms at the bottom of the deepest parts of the ocean. Until that time, many oceanographers felt that there could not possibly be enough food for anything to live in the far reaches of the sea bottom. The data collected aboard Challenger proved otherwise. One of the more interesting finds was a deep-sea glass sponge, a beautiful animal, as shown in the figure below. Nowadays, oceanographers realize that a rain of organic particles from the surface nourishes such animals, as well as the occasional large carcass, such as a dead whale or lost sailor, which provide food to bottom-dwelling scavengers.

 


Glass Sponge (left) and Radiolaria (right)

Plankton samples also proved to be a rich source of new discoveries. Many of the microscopic forms had not been seen previously and the extent of their habitat, from the surface of the sea to the deepest depths, was unexpected. The illustrations of these organisms are still widely used today and are of such detail and artistic quality that even non-planktologists marvel at their beauty. The radiolaria shown above are just one of the hundreds of examples. In total, Challenger scientists catalogued 4,717 new species, a staggering achievement. The next closest achievement in terms of finding new species has to be the late 1970s discovery of hundreds of new species of animals living on deep-sea hydrothermal vents and possibly, more recent explorations of the abyssopelagic environments with ROVs and submersibles. But even combined, these accomplishments don't nearly match the sheer numbers of new organisms brought to our attention by the Challenger.

One of the more intriguing measurement methods used by Challenger, that thankfully is not necessary today, was their method for determining the depth of the bottom. To accomplish the many tasks of towing nets, dredging the bottom, collecting water samples and determining depth, the ship needed a substantial amount of cable and lines. One report I saw mentioned 144 miles of hemp rope for sounding and 12.5 miles of piano wire on board for sampling (Duxbury reports this figure also). To determine the depth of the bottom (a process called sounding), a weight (weighing over 100 pounds) was attached to the rope and lowered to the bottom. The line was marked in intervals and the depth of the bottom determined. The deepest depth recorded by the Expedition was located in the Marianas Trench, a place now known as the Challenger Deep. At this location, the scientists measured a depth of 26,850 feet!

William Broad in his publication, The Universe Below (1997), recalls the words of another naturalist on board, Henry Mosely, who describes the evolution of feeling about this type of work.

At first, when the dredge came up, every man and boy who could possibly slip away, crowded 'round it, to see what had been fished up...Gradually, as the novelty of the thing wore off, the crowd became smaller and smaller, until at last only the scientific staff, and perhaps one or two other officers besides the one on duty, awaited the arrival of the net on the dredging bridge.

Such is the glamour of shipboard work! Indeed, many times the dredge or sounding rope would be lowered at 9 in the morning and not retrieved until 5 in the afternoon. Imagine being on watch making sure nothing happens to it. The hours do get long and tedious sometimes. But it's the possibility of discovering something that no one has seen before or no one has known before that makes you want to get up in the morning and do it all over again.

 

 
The Zoological Laboratory (left) and the Chemical Laboratory (right)

Listing the highlights and accomplishments of the Challenger Expedition are sort of like trying to list Albert Einstein's achievements in one sentence. Where do you start? The work of the 100+ scientists involved in the project occupied 50 volumes—29,552 pages—each volume as "thick as a family Bible", an accomplishment that took 23 years to complete.

That volume of knowledge notwithstanding, there are key discoveries reported by the expedition that deserve our attention. As reported by the Environmental News Network Daily News web site (I guess they're just catching up!), the major findings of the Challenger Expedition include:

  • the first systematic plot of currents and temperatures in the ocean;
  • a map of bottom deposits that has not been changed much by more recent studies;
  • an outline of the main contours of the ocean basins,
  • the discovery of the mid-Atlantic Ridge (which baffled scientists at the time)
  • the then record 26,900 feet (8,200 meters) Challenger Deep in the Mariana Trench;
  • the discovery of 715 new genera and 4,717 new species of ocean life forms; and
  • the discovery of prodigious life forms even at great depths in the ocean (refuting earlier hypotheses)

The Challenger was the first voyage to carry a camera. As such, the expedition was the first to have taken a photograph of an iceberg. However, the photographers did not supplant artists and their drawings. Scientific illustration reached a new peak with the Challenger voyage, with precise and detailed depictions of a range of sea creatures for the report’s 29,552 pages.

From huge fish to microscopic algae, the illustrations can be viewed as the first modern scientific illustrations. They were completed in painstaking detail, with a level of detail that still makes them invaluable today.

The Challenger Society provides these accolades:

At its completion, The Report discussed with full detail of text and illustrations the currents, temperatures, depths and constituents of the oceans, the topography of the sea bottom, the geology and biology of its covering and the animal life of the abyssal waters. The Challenger cruise had lain the cornerstone of scientific oceanography and begun its introduction to the wider scientific and lay community...The findings of the cruise were correctly described by John Murray in 1895 as "the greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries".

A prodigious number of observations laid the foundations for much of the oceanography to come. In one sense, the Challenger Expedition marked the arrival of oceanography as a science. Exploration and map-making would no longer take the primary role in ocean science. A new ocean science, encompassing physical, chemical, geological and biological studies was born.

Track of H.M.S. Challenger, December 1872 to May 1876, showing dredging and trawling stations

 

To see some examples of the many illustrations in the expedition report volumes go to the Challenger Report page.