In 1907 Wallace wrote the short book Is Mars Habitable? to criticize the claims made by Percival Lowell that there were Martian canals built by intelligent beings. Wallace did months of research, consulted various experts, and produced his own scientific analysis of the Martian climate and atmospheric conditions. Among other things Wallace pointed out that spectroscopic analysis had shown no signs of water vapor in the Martian atmosphere, that Lowell’s analysis of Mars’ climate was seriously flawed and badly overestimated the surface temperature, and that low atmospheric pressure would make liquid water, let alone a planet girding irrigation system, impossible.