Our Vision of Mars

Our Vision of Mars

Percival Lowell’s notebooks are full of what he thought he saw: bright and dark areas, a hint of polar caps, and canals, a planet festooned with canals. Lowell believed he was seeing a globe-girdling network of great irrigation ditches, carrying water from the melting polar caps to the thirsty inhabitants of the equatorial cities. He believed the planet to be inhabited by an older and wiser race, perhaps very different from us. He believed that the seasonal changes in the dark areas were due to the growth and decay of vegetation. He believed that Mars was, very closely, Earth-like. All in all, he believed too much.

Lowell conjured up a Mars that was ancient, arid, withered, a desert world. Still, it was an Earth-like desert. Lowell’s Mars had many features in common with the American Southwest, where the Lowell Observatory was located. He imagined the Martian temperatures a little on the chilly side but still as comfortable as the South of England. The air was thin, but the elegant network of canals carried the life-giving fluid all over the planet.

Our vision of Mars has a mythic quality as old as Genesis. Image: © Elena

What was in retrospect the most serious contemporary challenge to Lowell’s ideas came from an unlikely source. In 1907, Alfred Russel Wallace, co-discoverer of evolution by natural selection, was asked to review one of Lowell’s books. He had been an engineer in his youth and, while somewhat credulous on such issues as extrasensory perception, was admirable sceptical on the habitability of Mars.

Wallace showed that Lowell had erred in calculation of the average temperatures on Mars; instead of being as temperate as the South of England, they were, with few exceptions, everywhere below the freezing point of water. There should be permafrost, a perpetually frozen subsurface. The air was much thinner than Lowell had calculated. Craters should be as abundant as on the Moon. And as for the water in the canals:

Any attempt to make that scanty surplus of water, by means of overflowing canals, travel across the equator into the opposite hemisphere, through such terrible desert regions and exposed to such a cloudless sky as Mr. Lowell describes, would be the work of a body of madmen rather than of intelligent beings. It may be safely asserted that not one drop of water would escape evaporation or insoak at even a hundred miles from its source.

The devastating and largely correct physical analysis was written in Wallac’s eight-fourth year. His conclusion was that life on Mars – by this he meant civil engineers with an interest in hydraulics – was impossible. He offered no opinion on microorganisms.

The Great Mystery of the Martian Canals

When Paul Fox of Cornell and Carl Sagan compared Lowell’s maps of Mars with the Mariner 9 orbital imagery – sometimes with a resolution a thousand times superior to that of Lowell’s Earthbound twenty-four-inch refracting telescope – they found virtually no correlation at all. It was not that Lowell’s eye had stung up disconnected fine detail on the Martian surface into illusionary straight lines. There was no dark mottling of crater chains in the position of most of his canals. There were no features there at all. Then how could he have drawn the same canals years after years? How could other astronomers – some of who said they had not examined Lowell’s maps closely until after their own observations – had drawn the same canals?

One of the great findings of Mariner 9 mission to Mars was that there are time-variable streaks and splotches on the Martian surface – many connected with the ramparts of impact craters – which change with the seasons. They are due to windblown dust, the patterns varying with the seasonal winds. But the streaks do not have the character of the canals, they are not in the position of the canals, and none of them is large enough individually to be seen from the Earth in the first place. It is unlikely that there were real features on Mars even slightly resembling Lowell’s canals in the first few decades of this century that have disappeared without a trace as soon as close-up spacecraft investigations became possible.

Which side of the telescope the intelligence is on? Image: Colors © Megan Jorgensen (Elena)

The canals on Mars seem to be the same malfunction, under difficult seeing conditions, of the human hand/eye/brain combination (or at least for some humans; many other astronomers, observing with equally god instruments in Lowell’s time and after, claimed there were no canals whatever). But this is hardly a comprehensive explanation, and I have the nagging suspicion that some essential feature of the Martian canal problem still remains undiscovered.

Lowell always said that the regularity of the canals was an unmistakable sign that they were of intelligent origin. This is certainly true. The only unresolved question was which side of the telescope the intelligence was on.

Lowell’s Martians were benign and hopeful even a little godlike, very different from the malevolent menace posed by Wells and Welles in the War of the Worlds. Both sets of ideas passed into the public imagination through Sunday supplements and science fiction.