Editing Challenger Deep (section)

===1875 – HMS ''Challenger''===
In 1875, during her transit from the [[Admiralty Islands]] in the [[Bismarck Archipelago]] to [[Yokohama]] in Japan, the three-masted sailing corvette HMS ''[[HMS Challenger (1858)|''Challenger'']] ''attempted to make landfall at [[Spanish East Indies|Spanish Marianas]] (now [[Guam]]), but was set to the west by "baffling winds" preventing her crew from "visiting either the [[Caroline Islands|Carolines]] or the [[Mariana Islands|Ladrones]]."<ref>Spry, W.J.J., "The Cruise of the Challenger", 1877, p. 273</ref> Their altered path took them over the undersea canyon which later became known as the Challenger Deep. [[Sounding line|Depth soundings]] were taken by Baillie-weighted marked rope, and geographical locations were determined by [[celestial navigation]] (to an estimated accuracy of two nautical miles). One of their samples was taken within fifteen miles of the deepest spot in all of Earth's oceans. On 23 March 1875, at sample station number #225, HMS ''Challenger'' recorded the bottom at {{convert|4475|fathom|lk=on}} deep, (the deepest sounding of her three-plus-year eastward [[circumnavigation]] of the Earth) at {{Coord|11|24|N|143|16|E}} – and confirmed it with a second sounding at the same location.<ref name="Bathymetric mapping of the world's deepest seafloor, Challenger Deep"/> The serendipitous discovery of Earth's deepest depression by [[Challenger expedition|history's first major scientific expedition devoted entirely to the emerging science of oceanography]], was incredibly good fortune, and especially notable when compared to the Earth's third deepest site (the [[Sirena Deep]] only 150 nautical miles east of the Challenger Deep), which would remain undiscovered for another 122 years.