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.