Task: Question Generation
Input (English): Passage: The Imperial Trans-Antarctic Expedition of 1914–1917 is considered to be the last major expedition of the Heroic Age of Antarctic Exploration. Conceived by Sir Ernest Shackleton, the expedition was an attempt to make the first land crossing of the Antarctic continent. After Amundsen's South Pole expedition in 1911, this crossing remained, in Shackleton's words, the “one great main object of Antarctic journeyings”.  The expedition failed to accomplish this objective, but became recognized instead as an epic feat of endurance.
Shackleton had served in the Antarctic on the Discovery Expedition of 1901–1904, and had led the Nimrod Expedition of 1907–1909. In this new venture he proposed to sail to the Weddell Sea and to land a shore party near Vahsel Bay, in preparation for a transcontinental march via the South Pole to the Ross Sea. A supporting group, the Ross Sea party, would meanwhile establish camp in McMurdo Sound, and from there lay a series of supply depots across the Ross Ice Shelf to the foot of the Beardmore Glacier. These depots would be essential for the transcontinental party's survival, as the group would not be able to carry enough provisions for the entire crossing. The expedition required two ships: Endurance under Shackleton for the Weddell Sea party, and Aurora, under Aeneas Mackintosh, for the Ross Sea party.
Endurance became beset in the ice of the Weddell Sea before reaching Vahsel Bay, and drifted northward, held in the pack ice, throughout the Antarctic winter of 1915. Eventually the ship was crushed and sunk, stranding its 28-man complement on the ice. After months spent in makeshift camps as the ice continued its northwards drift, the party took to the lifeboats to reach the inhospitable, uninhabited Elephant Island. Shackleton and five others then made an 800-mile (1,300 km) open-boat journey in the James Caird to reach South Georgia. From there, Shackleton was eventually able to mount a rescue of the men waiting on Elephant Island and bring them home without loss of life. On the other side of the continent, the Ross Sea party overcame great hardships to fulfil its mission. Aurora was blown from her moorings during a gale and was unable to return, leaving the shore party marooned without proper supplies or equipment. Nevertheless, the depots were laid, but three lives were lost before the party's eventual rescue.
Output (English): What required two ships?