[[Image:Trieste (23 Jan 1960).jpeg|thumb| January 23, 1960: the Bathyscaphe Trieste just before the record dive. Behind her is the USS Lewis (DE 535). [[Image:Bathyscaphe Trieste Piccard-Walsh.jpg|thumb|Don Walsh and Jacques Piccard inside the Bathyscaphe Trieste.]]
Contents
Project Nekton was the codename for a series of very shallow test dives (three of them in Apra Harbor) and also deep-submergence operations in the Pacific Ocean near Guam that ended with the United States Navy-owned research bathyscaphe Trieste entering the Challenger Deep, the deepest surveyed point in the world's oceans.
The series of eight dives began with two harbor dives, then a Pacific ocean test dive at Guam, by the newly modified Trieste, which had been modified to dive far deeper than before. After two checkout dives, the first abyssal dive reached a record of 18,150 ft on November 15, 1959. The series included a record deep dive to near the bottom of the Nero deep in the Mariana Trench at 24,000 ft, and finally culminated with a trip to the bottom of the Challenger Deep at 35,797 feet, on January 23, 1960.
The project name was proposed by oceanographer Dr. Robert S. Dietz in early 1958, as plans to modify the Trieste bathyscaphe to go to the deepest part of the oceans were being contemplated. It is in reference to ocean life that actively swims (nekton) as opposed to the plankton organisms that only drift. The bathyscaphe Trieste to be used for Project Nekton was able to move independently, in contrast to tethered bathyspheres. The Trieste featured two electric motors, each with a propeller, of two horsepower each. These allowed it to move forward, backward and to turn horizontally. A maximum speed of 1 knot was attainable over a few miles distance.
Operations
Trieste departed San Diego on October 5, 1959 for Guam aboard the freighter SS Santa Mariana to participate in Project Nekton, a series of very deep dives near Guam, culminating in a descent to the Mariana Trench. It had been modified with a larger gasoline float, larger ballast tubs, and a newly designed heavy pressure sphere (made by Krupp in Germany), after having been purchased by the Office of Naval Research, which undertook the modification.
The first two test dives in the Nekton series were conducted at Guam in the Apra Harbor, then a third dive off the Western flank of Guam reached 4,900 ft.
The next dive, the fourth in the Nekton series, was a very deep dive (dive 61 in a long series of bathyscaphe dives supervised by Jacques Piccard). It reached 18,600 ft (later recalibrated to 18,150 feet) depth, to the sea floor, on November 15, 1959. On returning from this dive, some water leakage was noted along the seals between the three sections of the sphere, but since these were held together with pressure at depth, it was not considered serious after re-epoxying.
Dive 62 (eighth in the Nekton series) was another Apra Harbor dive. The next dive (sixth in the series, dive 63 for Piccard) was another checkout dive December 18, west of Guam. It reached 5,700 feet.
The next dive (dive 64 in a series, seventh in the Nekton series) reached 24,000 feet in the Nero Deep in the Mariana Trench 70 miles off Guam. This deep had been discovered in 1899 by the USS Nero in a search for a deep sea cable route to the orient. This dive did not quite reach the bottom, 48 feet below, because too much ballast had been released when the bottom was sounded, and once rising, the bathyscaphe could not be stopped.
On dive 65 (8th in the Nekton series), on January 23, 1960, Trieste reached the ocean floor in the Challenger Deep (the deepest southern part of the Mariana Trench), carrying Jacques Piccard (son of the boat's designer Auguste Piccard) and Lieutenant Don Walsh, USN. This was the first time a vessel, manned or unmanned, had reached the deepest point in the Earth's oceans. The onboard systems indicated a depth of 11,521 metres (37,799 ft), although this was later revised to 10,916 metres (35,814 ft) and more accurate measurements made in 1995 have found the Challenger Deep to be slightly shallower, at 10,911 metres (35,797 ft).
The descent to the ocean floor took 4 hours and 48 minutes at a descent rate of 0.914 m/s. After passing 9,000 metres one of the outer Plexiglas window panes cracked, shaking the entire vessel. The two men spent barely twenty minutes at the ocean floor, eating chocolate bars to keep their strength. The temperature in the cabin was a mere 7°C (45°F) at the time. While on the bottom at maximum depth, Piccard and Walsh unexpectedly regained the ability to communicate with the surface ship, USS Wandank II, using a sonar/hydrophone voice communications system. At a speed of almost a mile per second (about five times the speed of sound in air), it took about seven seconds for a voice message to travel from the craft to the surface ship and another seven seconds for answers to return.
While on the bottom, Piccard and Walsh observed a number of small sole and flounder swimming away, indicating that at least some vertebrate life can withstand the extremes of pressure in any of the Earth's oceans. They noted that the floor of the Challenger Deep consisted of "diatomaceous ooze". The ascent to surface took 3 hours, 15 minutes.
Successor exploration programs in the Challenger Deep
The next manned craft to reach the bottom of the Challenger Deep was Deepsea Challenger, on 25 March 2012. A Japanese robotic craft Kaikō reached the bottom of the Challenger Deep in 1995. The Nereus hybrid remotely operated vehicle (HROV) reached the bottom on May 31, 2009.