The greatest advance in the knowledge of our planet since the discoveries of the fifteenth and sixteenth centuries.
When the HMS Challenger set sail from Portsmouth on December 21, 1872, its crew had little idea they were embarking on what would become the foundation of modern oceanography 2 .
The expedition collected thousands of marine specimens, and today, 150 years later, these very collections are helping scientists solve some of the most pressing environmental issues of our time.
In the 19th century, the deep sea was one of Earth's last great mysteries. Many leading scientists, like Edward Forbes, believed that no life could exist below 300 fathoms (1,800 feet), dubbing it an "azoic zone" 3 . This theory was beginning to be challenged, and the Challenger Expedition, initiated by scientists William Benjamin Carpenter and Charles Wyville Thomson, was conceived to settle the debate 3 .
HMS Challenger departs from Portsmouth on its historic voyage
Three-and-a-half-year circumnavigation of the globe
Return with thousands of specimens and oceanographic data
Final volume of the 50-volume report published
The Royal Society of London and the Royal Navy converted a naval warship into a floating laboratory 1 . The ship's 17 guns were reduced to two to make space for scientific equipment.
To circumnavigate the globe, plumb the deepest oceans, and discover what, if anything, lived there, settling the debate about life in the deep sea.
The achievements of the Challenger expedition were staggering in their scale and significance.
The expedition resulted in a 50-volume report that took over 20 years to complete and became the bedrock of the new science of oceanography 5 .
"The greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries."
The Challenger was a marvel of scientific ingenuity, equipped with custom-built tools to probe the unknown deep. The work was methodical, with measurements and samples taken at hundreds of designated "stations" across the globe 5 .
| Tool | Function | Notable Fact |
|---|---|---|
| Sounding Line | A weighted rope to measure ocean depth. | Carried 181 miles (291 km) of Italian hemp rope 1 8 . |
| Dredge & Trawl | A net attached to an iron frame dragged along the seafloor to collect biological specimens 1 . | The beam of one trawl was crushed and broken by the immense pressure at 11,700 feet . |
| Buchanan Water Sampler | A sealed bottle that collected water from specific depths for chemical analysis . | Allowed for the first systematic study of ocean chemistry . |
| Specimen Jars | Glass jars filled with alcohol or brine to preserve biological samples for the journey home 1 . | Thousands of jars were stored on board; only three broke during the entire voyage 2 . |
The scientists then meticulously examined the "ooze" and specimens on deck, often to the bewilderment of the sailors 3 .
While the 19th-century discoveries were revolutionary, the true testament to the Challenger's foresight is that its specimens are still yielding new secrets today.
Dr. Stephen Stukins, a senior curator at the Natural History Museum, is using foraminifera—tiny plankton with shells—collected by the Challenger to study ocean acidification.
By comparing these 150-year-old shells with modern samples, his team discovered that the shells are now significantly thinner. "This thinning is due to ocean acidification as a result of increased carbon dioxide in the atmosphere," Stukins explains 2 .
The expedition was the first to collect micrometeorites from the ocean floor, the oldest such collection in the world 2 .
Today, scientists are also finding that the deep trenches discovered by the Challenger, like the Mariana, have become repositories for microplastics and toxic pollutants, showing that human impact has reached the most remote corners of the planet 6 .
The Challenger's specimens provide a critical historical baseline against which we can measure the decline of marine life. In Hawaii, the crew noted the introduction of invasive American birds and plants 2 .
Since then, at least 271 species have gone extinct on the islands, a trend the expedition documented in its earliest stages 2 .
The voyage of the HMS Challenger was more than a single expedition; it was the beginning of our continuous journey to understand the global ocean. The specimens its crew collected were not merely stored away but have become a time capsule, allowing scientists 150 years later to track the profound changes humanity has inflicted on the marine environment.
In an era of climate change and biodiversity loss, the Challenger's legacy is a powerful reminder that fundamental scientific exploration is not a relic of the past, but a crucial investment in our future. The deep sea is no longer an unknown abyss, but a known environment that requires our care—a truth we owe to the Victorian pioneers of the Challenger.