Without water there is no life, or at least life as we humans know and understand it. When in the nineteenth century people began to speak of the “Martians” as our closest likely cosmic neighbours, it was necessary to place them in a world with water. Luckily, the data available at the time supported the notion: the presence of polar ice caps on Mars was known from the observations of Cassini and Huygens two centuries earlier, and in 1784 William Herschel ventured the existence of oceans and a “modest” atmosphere, which give its people “a situation in many respects similar to our own.”
In 1877, the Italian Giovanni Schiaparelli drew a map of Mars showing seas and channels. It was not difficult for the human imagination to populate that geography with intelligent beings capable of constructing engineering works. The first speculation that the channels could be artificial was published by the French astronomer and author Camille Flammarion, first in his novel Uranie (1889), and then in his essay La planète Mars et ses conditions d’habitabilité (1892). Flammarion conceived the idea of a blighted planet, irrigated by a network of canals.
Flammarion’s essay came into the hands of an amateur astronomer, a wealthy Bostonian named Percival Lowell (13 March 1855 – 12 November 1916) who had travelled extensively in the Far East. After reading Flammarion, Lowell returned to his country in 1893 in order to devote the rest of his life to astronomy. The following year, he founded his own observatory in Flagstaff, in the remote territory of Arizona.
The theory of canals on Mars
Lowell not only had an idea and the money to fund it, he also had a knack for popularization, which for the current director of the Lowell Observatory, Jeffrey Hall, made him “the Carl Sagan of his day,” he tells OpenMind. The Bostonian became the champion of the theory of the canals, which he developed and accompanied with his own drawings in three books: Mars (1895), Mars and Its Canals (1906) and Mars As the Abode of Life (1908).
A translation error is often cited as the origin of the idea of the canals. Schiaparelli used the Italian word canali, which does not distinguish between natural and artificial structures as the English words “channels” and “canals” do. However, for Hall, “Lowell was not confused.” “Schiaparelli thought he saw channels, but Lowell thought they were not channels, but canals of intelligent origin.” According to the director of the observatory, Lowell held the idea that there was a Martian civilization, and thus the canals were part of his theory, “just a genuine hypothesis that turned out to be incorrect.”
Lowell’s idea caught on among the public. Meanwhile, other scientists claimed that Mars was too cold and dry to support a network of rivers. In fact, no one else could see the canals that Lowell had drawn. So, how did he see them? “There are definitely markings on Mars’s surface, and I believe this is a case of looking for so long, and so diligently, that Lowell convinced himself the canals were there when in fact they were not,” says Hall. “As a scientist myself, I know this is an all-too-common pitfall: we have to be very careful to look for the answer that is there, not the answer we think should be there.”
Inspiration for the ‘War of the Worlds’
Lowell’s canals exerted a powerful influence on the popular iconography of Mars. “He inspired many scientists as well as science fiction writers, and contributed immensely to public interest in astronomy and the cosmos,” assesses Hall. Even H. G. Wells, the author of the most renowned literary Martian invasion, War of the Worlds (1898), would describe the theory of his “friend” Lowell as “very convincing.” Even in 1950, Ray Bradbury would rescue the image of the canals in his Martian Chronicles.
Although Lowell’s canals and a Martian civilization were quickly dismissed by the scientific community, the fact is that the definitive visual confirmation that all this was a fantasy did not come until the arrival of the first images of the surface by NASA’s Mariner 4 probe in 1965. Paradoxically, at the same time, the idea of water on Mars was beginning to become a reality: in 1963, a study confirmed that the Martian atmosphere contains water vapour, something that many scientists had already discarded.
Since then, the search for water on Mars has become an intense scientific saga. In 2004, NASA’s Opportunity rover confirmed in situ that our neighbouring planet retains abundant geological and geographical traces of a wet past with rivers and oceans. Soon after, someone left a glass of champagne at the mausoleum of Lowell. In 2008, the Phoenix robot directly verified the presence of frozen water under a thin layer of soil in the Martian Arctic.
No evidences of liquid water
Liquid water has been more elusive to find. Between the intense Martian cold and the weak atmosphere that reduces the boiling point of pure water to just 10°C, a liquid phase could occur only fleetingly and in special cases, such as in the form of a highly concentrated brine. This is precisely what a NASA study conducted by the University of Arizona suggested in 2011. According to researchers, some seasonal markings on the Martian slopes, similar to gullies and named Recurring Slope Lineae (RSL), are the result of flowing liquid water with a high salt content. In 2015, scientists found support for this hypothesis with a spectrum analysis of deposits that revealed the presence of hydrated salts.
Nonetheless, the debate continues. Last August, a thermal analysis of images taken by the orbiting Mars Odyssey concluded that the water content of the RSL is similar to “the driest desert sands of Earth,” in the words of the co-author of the study Christopher Edwards of the University of Northern Arizona. “Some type of water-related activity at the uphill end still might be a factor in triggering RSL, but the darkness of the ground is not associated with large amounts of water, either liquid or frozen,” Edwards said, concluding: “Totally dry mechanisms for explaining RSL should not be ruled out.”
The answer could be within the reach of Curiosity, the latest rover sent to Mars by NASA. The robot is currently in a zone of possible RSL, and NASA is toying with the idea of moving the rover nearer to one of them for a closer inspection. But what if there really were liquid water? And what if it actually harboured microbial life? The possibility that the residual microbes from the Curiosity could contaminate a favourable Martian location for life complicates the decision. On the other hand, there is something quite clear: if water flows finally do exist on Mars inhabited by Martians of some kind, Lowell deserves another glass of champ.