Which Russian icebreaker expedition located Litke Deep in 1955?

The Russian icebreaker expedition that located Litke Deep in 1955 was the Fyodor Litke expedition.

The expedition used the Soviet icebreaker Fyodor Litke for Arctic hydrographic work. Its 1955 campaign reached far into the Arctic Ocean and identified the deep later known as Litke Deep, or the Litke Depression. The feature is named for Fyodor Petrovich Litke, the Russian navigator, geographer, and Arctic explorer—not solely for the ship itself.

The vessel had a long career. Built in England in 1909 as the Canadian icebreaker Earl Grey, it was later transferred to Russia and renamed for Litke. It became especially noted for Arctic operations, including the first complete westbound passage of the Northern Sea Route in a single season in 1934.

The reported depth of Litke Deep is about 5,449 metres. It is not the Arctic Ocean’s deepest point by modern bathymetric ranking—that distinction is generally assigned to Molloy Deep—but its high-latitude position makes it especially notable: the seafloor there is often described as the point closest to Earth’s center because Earth is flattened at the poles.