This Day in History: August 12, 1877

On August 12, 1877, astronomer Asaph Hall discovered the the Martian moon Deimos while working at the United States Naval Observatory in Washington, D.C. Within a week, Hall also discovered Phobos, the second moon of Mars. Of the two moons, Deimos is the smaller and outermost. The two moons are also named after the Greek gods of terror (Deimos) and horror (Phobos), both of whom were children of the Greek god of war Ares (known as Mars in Roman mythology).