Editing Challenger Deep (section)

===Uncrewed descents by ROVs===

====1996 and 1998 – ''Kaikō''====
{{Main|Kaikō ROV}}

The remotely operated vehicle (ROV) ''Kaikō'' made many uncrewed descents to the Mariana Trench from its support ship RV ''Yokosuka'' during two expeditions in 1996 and 1998.<ref>{{cite web|url=https://www.mbari.org/wp-content/uploads/2016/01/Barry-and-Hashimoto-Challenger-deep-2009.pdf |archive-url=https://web.archive.org/web/20161220205139/https://www.mbari.org/wp-content/uploads/2016/01/Barry-and-Hashimoto-Challenger-deep-2009.pdf |archive-date=2016-12-20 |url-status=live |title=Revisiting the Challenger Deep using the ROV Kaiko |publisher=Winter 2009 Volume 43, Number 5 |access-date=15 December 2016}}</ref>
From 29 February to 4 March the ROV ''Kaiko'' made three dives into the ''central'' basin, ''Kaiko'' #21 – ''Kaiko'' #23, . Depths ranged from {{convert|10898|m|ft}} at {{Coord|11|22.536|N|142|26.418|E}}, to {{convert|10896|m|ft}} at {{Coord|11|22.59|N|142|25.848|E}}; dives #22 & #23 to the north, and dive #21 northeast of the deepest waters of the ''central'' basin.<ref>{{cite web| url = http://www.godac.jamstec.go.jp/darwin/dive/kaiko/21/e| title = Partial suspension of access to the data and services on our website < About JAMSTEC < JAMSTEC| access-date = 17 November 2019| archive-date = 17 November 2019| archive-url = https://web.archive.org/web/20191117232748/http://www.godac.jamstec.go.jp/darwin/dive/kaiko/21/e| url-status = live}}</ref> During the 1996 measurements the temperature (water temperature increases at great depth due to adiabatic compression), [[salinity]] and water pressure at the sampling station was {{convert|2.6|°C|°F}}, 34.7‰ and {{convert|1113|bar|MPa psi|abbr=on}}, respectively at {{convert|10897|m|0|abbr=on}} depth.<ref name="Akimoto">{{Cite journal| author=Akimoto | title=The deepest living foraminifera, Challenger Deep, Mariana Trench | journal=Marine Micropaleontology | volume=42 | issue=1–2 | year=2001 | page=95 | doi=10.1016/S0377-8398(01)00012-3|display-authors=etal| bibcode=2001MarMP..42...95A}}</ref> The Japanese robotic deep-sea probe ''Kaikō'' broke the depth record for uncrewed probes when it reached close to the surveyed bottom of the Challenger Deep. Created by the [[Japan Agency for Marine-Earth Science and Technology|Japan Agency for Marine-Earth Science and Technology (JAMSTEC)]], it was one of the few uncrewed deep-sea probes in operation that could dive deeper than {{convert|6000|m}}. The manometer measured depth of {{convert|10911.4|m|0|abbr=on}} ±{{convert|3|m|ft|0|abbr=on}} at {{Coord|11|22.39|N|142|35.54|E}} for the Challenger Deep is believed to be the most accurate measurement taken up to then.<ref>{{cite web |url=http://www.jamstec.go.jp/e/about/equipment/ships/kaiko7000.html |title=Kaiko 7000II |publisher=Japan Agency for Marine-Earth Science and Technology – note: this ref. contains a date error |access-date=26 March 2012 |archive-date=10 April 2020 |archive-url=https://web.archive.org/web/20200410211118/http://www.jamstec.go.jp/e/about/equipment/ships/kaiko7000.html |url-status=live }}</ref><ref name="Bathymetric mapping of the world's deepest seafloor, Challenger Deep"/>
Another source states the greatest depth measured by ''Kaikō'' in 1996 was {{convert|10898|m|0|abbr=on}} at {{Coord|11|22.10|N|142|25.85|E}} and {{convert|10907|m|0|abbr=on}} at {{Coord|11|22.95|N|142|12.42|E}} in 1998.<ref name="Bathymetric mapping of the world's deepest seafloor, Challenger Deep"/>
The ROV ''Kaiko'' was the first vehicle to visit to the bottom of the Challenger Deep since the bathyscaph ''Trieste'''s dive in 1960, and the first success in sampling the trench bottom sediment/mud, from which ''Kaiko'' obtained over 360 samples.<ref>Nakanishi, M., "A Precise Bathymetric map of the World's deepest seafloor, Challenger Deep in the Mariana Trench," Marine Geophysical Research, Table 2, 2011, p. 1</ref> Approximately 3,000 different microbes were identified in the samples.<ref>Cruise Summary, YK09-08, Taishi Tsubouchi "Challenger Area" p. 11</ref><ref name="ngnews">[http://news.nationalgeographic.com/news/2005/02/0203_050203_deepest.html "Life Is Found Thriving at Ocean's Deepest Point"] {{Webarchive|url=https://web.archive.org/web/20120822121902/http://news.nationalgeographic.com/news/2005/02/0203_050203_deepest.html |date=22 August 2012 }}, National Geographic News, 3 February 2005</ref><ref name="Akimoto"/>
''Kaikō'' was lost at sea off [[Shikoku|Shikoku Island]] during [[2003 Pacific typhoon season#Typhoon Chan-hom|Typhoon Chan-Hom]] on 29 May 2003.

====2009 – ''Nereus''====
[[File:Nereus (underwater vehicle) hydro20100720-full.jpg|thumb|HROV Nereus]]

{{Main|Nereus (underwater vehicle)}}
From 2 May to 5 June 2009, the RV ''Kilo Moana'' hosted the [[Woods Hole Oceanographic Institution]] ([[Woods Hole Oceanographic Institution|WHOI]]) hybrid remotely operated vehicle (HROV) ''[[Nereus (underwater vehicle)|Nereus]]'' team for the first operational test of the ''{{ship||Nereus|underwater vehicle|2}}'' in its 3-ton tethered ROV mode. The ''Nereus'' team was headed by the Expedition Leader Andy Bowen of WHOI, Louis Whitcomb of [[Johns Hopkins University]], and Dana Yoerger, also of WHOI. The expedition had co-chief scientists: biologist Tim Shank of WHOI, and geologist Patricia Fryer of the University of Hawaii, to head the science team exploiting the ship's [[bathymetry]] and organizing the science experiments deployed by the ''Nereus''.<ref>{{cite web| url = https://www.whoi.edu/press-room/news-release/hybrid-remotely-operated-vehicle-nereus-reaches-deepest-part-of-the-ocean/| title = Hybrid Remotely Operated Vehicle Nereus Reaches Deepest Part of the Ocean| access-date = 28 November 2019| archive-date = 12 April 2019| archive-url = https://web.archive.org/web/20190412164352/https://www.whoi.edu/press-room/news-release/hybrid-remotely-operated-vehicle-nereus-reaches-deepest-part-of-the-ocean/| url-status = live}}</ref> From ''Nereus'' dive #007ROV to {{convert|880|m|0|abbr=on}} just south of Guam, to dive #010ROV into the [[Mariana Trench|Nero Deep]] at {{convert|9050|m|0|abbr=on}}, the testing gradually increased depths and complexities of activities at the bottom.

Dive #011ROV, on 31 May 2009, saw the ''Nereus'' piloted on a 27.8-hour underwater mission, with about ten hours transversing the ''eastern'' basin of the Challenger Deep – from the south wall, northwest to the north wall – streaming live video and data back to its mothership. A maximum depth of {{convert|10902|m|0|abbr=on}} was registered at {{Coord|11|22.10|N|142|35.48|E}}. The ''{{ship|RV|Kilo Moana}}'' then relocated to the ''western'' basin, where a 19.3-hour underwater dive found a maximum depth of {{convert|10899|m|0|abbr=on}} on dive #012ROV, and on dive #014ROV in the same area (11°19.59 N, 142°12.99 E) encountered a maximum depth of {{convert|10176|m|0|abbr=on}}. The ''Nereus'' was successful in recovering both sediment and rock samples from the ''eastern'' and the ''western'' basins with its manipulator arm for further scientific analysis. The HROV's final dive was about {{convert|80|nmi|km|1|abbr=on}} to the north of the Challenger Deep, in the [[backarc]], where they dived {{convert|2963|m|0|abbr=on}} at the TOTO Caldera (12°42.00 N, 143°31.5 E).<ref name="unols.org">{{cite web| url = https://www.unols.org/sites/default/files/200912desap15.pdf| title = Operations of the Nereus Underwater Robotic Vehicle, DESSC, 13 December 2009| access-date = 28 November 2019| archive-date = 28 November 2019| archive-url = https://web.archive.org/web/20191128055501/https://www.unols.org/sites/default/files/200912desap15.pdf| url-status = live}}</ref><ref name="Robot sub reaches deepest ocean">{{cite news|url=http://news.bbc.co.uk/2/hi/science/nature/8080324.stm|title=Robot sub reaches deepest ocean|date=3 June 2009|access-date=3 June 2009|work=BBC News|archive-date=30 October 2019|archive-url=https://web.archive.org/web/20191030165503/http://news.bbc.co.uk/2/hi/science/nature/8080324.stm|url-status=live}}</ref> Nereus thus became the first vehicle to reach the Mariana Trench since 1998 and the deepest-diving vehicle then in operation.<ref name="Robot sub reaches deepest ocean"/> Project manager and developer Andy Bowen heralded the achievement as "the start of a new era in ocean exploration".<ref name="Robot sub reaches deepest ocean"/> ''Nereus'', unlike ''Kaikō'', did not need to be powered or controlled by a cable connected to a ship on the ocean surface.<ref name="Nereus">{{cite web|url=http://www.physorg.com/news163167519.html|title='Nereus' reaches deepest part of the ocean|date=2 June 2009|access-date=2 June 2009|publisher=physorg.com|archive-date=6 June 2011|archive-url=https://web.archive.org/web/20110606085530/http://www.physorg.com/news163167519.html|url-status=live}}</ref><ref name="Daily Reports for R/V KILO MOANA" /><ref name="Robot sub reaches deepest ocean"/><ref name="Daily Reports for R/V KILO MOANA April and May 2009">{{Cite news|url=http://www.soest.hawaii.edu/UMC/cms/ship-daily-reports/|title=Daily Reports for R/V KILO MOANA April and May 2009|date=31 May 2009|publisher=University of Hawaii Marine Center|access-date=31 May 2009|archive-date=31 December 2013|archive-url=https://web.archive.org/web/20131231001444/http://www.soest.hawaii.edu/UMC/cms/ship-daily-reports/|url-status=dead}}</ref><ref name="Nereus Mission">{{Cite news|url=http://www.whoi.edu/page.do?pid=7545&tid=282&cid=57586&ct=162|title=Hybrid Remotely Operated Vehicle "Nereus" Reaches Deepest Part of the Ocean|date=2 June 2009|publisher=Woods Hole Oceanographic Institution|access-date=2 June 2009|archive-date=13 July 2009|archive-url=https://web.archive.org/web/20090713052319/http://www.whoi.edu/page.do?pid=7545&tid=282&cid=57586&ct=162|url-status=live}}</ref><ref name="unols.org"/>
The HROV ''Nereus'' was lost on 10 May 2014 while conducting a dive at {{convert|9900|m|ft}} in depth in the [[Kermadec Trench]].<ref>{{cite news|url=https://www.bbc.com/news/science-environment-27374326|title=Deep-sea sub 'implodes' 10&nbsp;km-down|first=Jonathan|last=Amos|work=BBC News|date=12 May 2014|access-date=21 July 2018|archive-date=7 July 2018|archive-url=https://web.archive.org/web/20180707183011/https://www.bbc.com/news/science-environment-27374326|url-status=live}}</ref>