Marvin was given the role of chief scientist and keeper of the ship's log. He would record the day-to-day activities of the men, and of the general conditions that the men had to face while headed toward the arctic, which included the weather. Marvin kept a journal of his days on the ice, however the entries began to dwindle as the expedition went on. His last journal entry was on December 8, 1908. On this journey, they were better equipped. They had 7 explorers, 17 Eskimos, 133 sled dogs, and 19 sledges. There was a main group and there were smaller groups. The smaller groups would break off from the main group and go ahead to establish camps for the main group. While Peary set out to reach the North Pole, Marvin was left behind as part of a staged support team. His partners were Inuit cousins, Kudlookto and Harrigan. After Peary left Marvin with his two Eskimo companions, Peary never saw Marvin alive.