[Cross-posted at Cliopatria.]
Via Bad Astronomy comes news of an update to the Mars component of Google Earth. Most interesting to me are the overlays of historical maps of Mars from the 19th and 20th centuries, including those made by Giovanni Schiaparelli (1890), Percival Lowell (1896) and E. M. Antoniadi (1909). Schiaparelli and Lowell's maps showed the infamous canals of Mars; Antoniadi's more detailed map did not, and is supposed to have finished off the canals as a scientific controversy, at least according to according to Steven J. Dick's brilliant history The Biological Universe: The Twentieth-Century Extraterrestrial Life Debate and the Limits of Science (Cambridge: Cambridge University Press, 1996). But from some of my own work I've seen evidence that the canals and the associated question of intelligent life on Mars survived into the 1920s. And now Google Earth shows me this beautiful map made by the US Air Force in 1962. This Mars was festooned with canals, half a century after they had largely been discarded by the scientific community.
A little digging shows why. The map, known as the MEC-1 prototype, was prepared to assist with the upcoming Mariner missions to Mars. E. C. Slipher, late director of the Lowell Observatory (a major centre for planetary research), helped make it. Slipher had got his start under Lowell himself in the late 1900s, and used his mentor's old observations to compile MEC-1. So it's no surprise it has canals, then. Slipher seems to have remained an advocate of the canals right up until his death in 1964. Perhaps fortunately for him, he didn't live to witness Mariner 4's flyby of Mars in 1965, which revealed an apparently dead planet. But if it had not, the USAF would have been well placed to explore the Martian megascale hydraulic system.