Mars - Inhabited Or Not?

Lowell's ideas were not shared by most astronomers of the time. In 1908 the distinguished journal Scientific American noted that "Lowell is practically alone in the astronomical world in believing that he has proven that Mars is inhabited."

Scientists pointed out that artificial canals would have to be hundreds of miles wide to be visible from Earth. Furthermore, Mars was believed to be extremely cold, because of its great distance from the Sun. This made it even more unlikely that open flowing water was present on the planet's surface. Agnes Clerk (1842–1907) was a science writer trained in astronomy who wrote well-respected books about astronomical discoveries. She called Lowell's idea "hopelessly unworkable."

Lowell did have his supporters. The French astronomer Camille Flammarion (1842–1925) also believed that the lines on Mars were artificial canals built by an advanced civilization. Flammarion insisted that the reddish appearance of Mars was due to the growth of red vegetation on the planet.

In 1907 natural scientist Alfred Russel Wallace (1823–1913) wrote the book Is Mars Habitable?, which examined Lowell's claims one by one and attacked them with scientific data and reasoning. The book is considered a pioneering work in the field of exobiology (the investigation of possible life outside the Earth).

Wallace argued that Mars was a frozen desert and that the polar caps were probably frozen carbon dioxide, instead of water ice. Wallace ended the book with the following definitive statement: "Mars, therefore, is not only uninhabited by intelligent beings such as Mr. Lowell postulates, but is absolutely UNINHABITABLE."

Many astronomers of the time admitted seeing fine lines on the Martian surface. Most believed that these lines were either natural geological features or an optical illusion. Astronomer W. H. Pickering (1858–1938) believed the lines to be cracks in Mars's volcanic crust. He speculated that hot gases and water escaped through the cracks and supported vegetative growth. This explained the appearance of different-colored splotches on the planet. The general public and science fiction writers much preferred Lowell's explanation.