The Gusev Crater was named in 1876 after Russian astronomer Matvei Gusev (1826–1866). The crater (created by a large meteorite impact approximately 3.9 billion years ago during the Late Heavy Bombardment) is located 175.4°E 14.6°S, just south of the equator. It is 144 km (90 mi) in diameter and provided an ideal landing zone for one of the Mars Exploration Rover Mission rovers, Spirit.
An ancient lake?
The crater exhibits evidence that it once contained substantial quantities of liquid water. A channel enters the south of the crater. Known as Ma'adim Vallis, this was almost certainly a means for which the crater was supplied with water. On January 9th, 2004, the Spirit rover landed in the crater and began to analyse the surrounding rock. Expecting to find overwhelming evidence of an ancient lake, mission scientists were disappointed to find very little indication of water.