Throughout the 19th and 20th Centuries scientists believed that Mars had once been an Earth like place, with a thick atmosphere and water flowing through green valleys.

The running theme of former life on Mars was given a boost when, in 1894, Percivaal Lowell made his first rudimentary sketches of the ‘canals’of Mars' southern hemisphere. These canals had been observed by many astronomers and were believed, at the time, to be the vast irrigation system of an ancient civilization.