2009 – RV "Yokosuka" – Cruise YK09-08 brought the JAMSTEC 4,429-ton research vessel "Yokosuka" back to the Mariana Trough and to the Challenger Deep June–July 2009. Their mission was a two-part program: surveying three hydrothermal vent sites in the southern Mariana Trough backarc basin near 12°57’N, 143°37’E about 130 nmi northeast of the central basin of the Challenger Deep, using the autonomous underwater vehicle "Urashima". AUV "Urashima" dives #90-94, were to a maximum depth of 3500 meters, and were successful in surveying all three sites with a Reson SEABAT7125AUV multibeam echosounder for bathymetry, and multiple water testers to detect and map trace elements spewed into the water from hydrothermal vents, white smokers, and hot spots. Kyoko OKINO from the Ocean Research Institute, University of Tokyo, was principal investigator for this aspect of the cruise.