Gale is a crater on Mars near the northwestern part of the Aeolis quadrangle at (5.4°S 137.8°E). It is 154 km (96 mi) in diameter and estimated to be about 3.5-3.8 billion years old. The crater was named after Walter Frederick Gale, an amateur astronomer from Sydney, New South Wales, Australia, who observed Mars in the late 19th century. Aeolis Mons is a mountain in the center of Gale and rises 5.5 km (18,000 ft) high. Aeolis Palus is the plain between the northern wall of Gale and the northern foothills of Aeolis Mons.