The explorer is a man of restraint and of moral compunction. He is rather aghast at discovering the process of "justice" on the penal colony. Hearing that the man to be put to death has not only been denied a trial but has not even been told what his has been accused of, the explorer can hardly believe the nature of the system he has been invited to witness.
The explorer is a foreign traveler, visiting the penal colony on, and as a visitor he refrains from directly expressing his opinions of the execution until he is asked directly for his comments. He speaks diplomatically, but directly addresses his negative feelings for the process he has witnessed. He is not, however, interested in intevening any more than is strictly necessary. Thus he does not interfere with the initial execution, nor does he move to stop the officer from executing himself.
He is "fundamentally honorable and unafraid," but he does not intervene during the execution or when the officer takes his own life. (eNotes)
The explorer's sense of propriety and of being an outsider are both significant elements of his character.