On 31 May 2009 the United States sent the Nereus hybrid remotely operated vehicle (HROV) to the Challenger Deep.[13] Nereus thus became the first vehicle to reach the Mariana Trench since 1998 and the deepest-diving vehicle currently in operation.[13] Project manager and developer Andy Bowen heralded the achievement as "the start of a new era in ocean exploration".[13] Nereus, unlike Kaikō, did not need to be powered or controlled by a cable connected to a ship on the ocean surface.[14]
Nereus spent over 10 hours at the bottom of the Challenger Deep and measured a depth of 10,902 m (35,768 ft), while sending live video and data back to its mothership RV Kilo Moana at the surface and collecting geological and biological samples from the Challenger Deep bottom with its manipulator arm for further scientific analysis.[1][13][15][16]
The Nereus is operated by the Woods Hole Oceanographic Institution.
[edit] Lifeforms
The Summary Report of the HMS Challenger expedition lists radiolaria from the two dredged samples taken when the Challenger Deep was first discovered.[17] These (Nassellaria and Spumellaria) were reported in the Report on Radiolaria (1887) [18] written by Ernst Haeckel.
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.[19] The report has since been questioned, with suggestions that it may have been a sea cucumber. The video camera on board the Kaiko probe spotted a sea cucumber, a scale worm and a shrimp at the bottom.[20][21] At the bottom of the Challenger deep, the Nereus probe spotted one polychaete worm (a multi-legged predator) about an inch long.[22]
An analysis of the sediment samples collected by Kaiko found large numbers of simple organisms at 10,900 m (35,800 ft).[23] 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 distinct from those in shallower ecosystems.
The overwhelming majority of the organisms collected were simple, soft-shelled foraminifera (432 species according to National Geographic[24]), with four of the others representing species of the complex, multi-chambered genera Leptohalysis and Reophax. Eighty-five percent of the specimens were organic, soft-shelled allogromiids, which 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%. As small organisms with hard, calcareous shells have trouble growing at extreme depths because of the high solubility of calcium carbonate in the pressurized water, scientists theorize that the preponderance of soft-shelled organisms in the Challenger Deep may have resulted from the typical biosphere present when the Challenger Deep was shallower than it is 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.[citation needed] The species that survived the change in depth were the ancestors of the Challenger Deep's current denizens.
Bookmarks