Everything about The Challenger Deep totally explained
The
Challenger Deep is the deepest surveyed point in the oceans, with a depth of about 11,000 metres (about 36,000 feet). It is located in the
Mariana Islands group at the southern end of the
Mariana Trench. The closest land is
Fais Island, one of the outer islands of
Yap, 289 km southwest and
Guam 306 km to the northeast. The point is named after the British
Royal Navy survey ship
HMS Challenger, which first surveyed the trench in 1951.
Surveys and descents
The maximum surveyed depth of the Challenger Deep is 10,923 meters (35,838 feet) or 6.7875 miles. (National Geographic puts the depth at 10,920.07 meters (35,827 feet) below sea level.) The pressure at this depth is approximately 1,095 times that at the surface, or over 16,000 pounds per square inch (110 MPa).
The HMS
Challenger Expedition (December 1872 – May 1876) first sounded the depths now known as the Challenger Deep. This first sounding was made on
23 March, 1875 at
station 225
. The reported depth was 4,475
fathoms (8,184 m, 26,850 ft), based on two separate soundings.
A 1912 book,
The Depths of the Ocean by Sir John Murray, records the depth of the Challenger Deep as 9,635.9472 meters (31,614 feet). Sir John was one of the Expedition scientists, a young man at the time. Page
131 of Murray's book refers to the Challenger Deep. All of the original reports of the
Challenger expedition can be viewed on the web at the
Challenger Library.
In 1951, about 75 years after its original discovery, the entire
Mariana Trench was surveyed by a second
Royal Navy vessel, also named
HMS Challenger after the original expedition ship. During this survey, the deepest part of the trench was recorded using
echo sounding, a much more precise and vastly easier way to measure depth than the sounding equipment and drag lines used in the original expedition. HMS
Challenger measured a depth of 5,960
fathoms (10,900 m, 35,760 ft) at .
On 23 January 1960, the Swiss-built
Bathyscaphe Trieste, acquired by the
U.S. Navy, descended to the ocean floor in the trench manned by
Jacques Piccard (who co-designed the submersible along with his father,
Auguste Piccard) and USN Lieutenant
Don Walsh. The descent took almost five hours and the two men spent barely twenty minutes on the ocean floor before undertaking the three-hour-and-fifteen-minute ascent. They measured the depth as 10,916 metres (35,813 feet).
In 1984, a Japanese survey vessel using a narrow, multi-beam
echo sounder took a measurement of 10,924 meters (35,838 feet).
On 24 March, 1995 the Japanese
robotic deep-sea probe
Kaiko broke the depth record for uncrewed probes when it reached close to the surveyed bottom of the Challenger Deep. Created by the Japan Marine Science and Technology Center
(JAMSTEC) it was one of few uncrewed deep-sea probes in operation that could dive deeper than 6,000 metres (19,680 feet). Its recorded depth of 10,911 m (35,797 ft) for the Challenger Deep is believed to be the most accurate measurement taken yet.
Kaiko also collected a sediment core from the bottom of the deep.
Lifeforms
On their 1960 descent, the crew of the
Trieste noted that the floor consisted of
diatomaceous ooze and reported observing "some type of flatfish, resembling a
sole, about 1 foot long and 6 inches across" lying on the seabed. The fish sighting has since been questioned by some, however, with suggestions that it may possibly have been a
sea cucumber. The video camera on board the
Kaiko probe spotted a sea cucumber, a
scale worm (a type of
bristle worm) and a
shrimp at the bottom.
An analysis of the sediment samples collected by
Kaiko announced the discovery of large numbers of simple organisms at 10,900 metres water depth. While similar lifeforms have been known to exist in shallower ocean trenches (>7,000 m) and on the
abyssal plain, the lifeforms discovered in the Challenger Deep possibly represent
taxa independent from those in shallower ecosystems.
Out of the 432 organisms collected, the overwhelming majority of the sample consisted of simple, soft-shelled
foraminifera, with four of the others representing species of the complex, multi-chambered genera
Leptohalysis and
Reophax. Overall, 85% of the specimens consisted of organic soft-shelled allogromids. This is unusual compared to samples of sediment-dwelling organisms from other deep-sea environments, where the percentage of organic-walled foraminifera ranges from 5% to 20% of the total. As small organisms with hard calcated shells have trouble growing at extreme (10,000 m) depths because the water there's severely lacking in
calcium carbonate, scientists theorize that the preponderance of soft-shelled organisms at the Challenger Deep may have resulted from the typical
biosphere present when the Challenger Deep was shallower than it's now. Over the course of six to nine million years, as the Challenger Deep grew to its present depth, many of the species present in the sediment died out or were unable to adapt to the increasing water pressure and changing environment. The remaining species may have been the ancestors of the Challenger Deep's current denizens.
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