What caused the canals on Mars? Why was Mars said to have canals?

Why was Mars said to have canals?

On Hallowe’en Night, 1938, radio listeners in New York were startled to hear a man’s voice saying, ‘Ladies and gentlemen, I have a grave announcement to make. Incredible as it may seem, strange beings who landed in Newjersey tonight are the vanguard of an invading army from Mars.’ Orson Welles, doing a radio dramatisation of the H. G. Wells novel, The War ofthe Worlds, sent his audience into a panic. For more than sixty years, the notion that there might be life on Mars had been spreading. In 1877, Italian astronomer Giovanni Schiaparelli said that he had identified canali on the Red Planet.

In Italian, canali means ‘grooves’ or ‘channels'. But the word was translated into English as canals and the myth was up and running. Canals signified intelligent life; beings lived on Mars who were capable of carrying out vast engineering projects and even of building spaceships with which to invade and attack the Earth. Popular science articles surmised that these canals were designed perhaps to save a dying planet by transporting water from the poles to the arid heartland. The argument had some logic. Because gravity on Mars is low, only about two fifths that on Earth, water vapour in the atmosphere soon leaks into space. The planet, said the pop scientists, had a perpetual problem to stop its farmlands from drying out, and its engineers were solving it.

Once one astronomer had seen canali, others saw them too. Percival Lowell, a wealthy American astronomer, set up his own observatory in Flagstaff, Arizona, took hundreds of photographs and, in 1896, published maps of Mars showing a network of some 500 canals or aqueducts. These, he reasoned, were used to supply water for irrigation.

Helping to cloak the planet in mystery was the difficulty of seeing it clearly. Earth’s turbulent atmosphere and Mars’s frequent dust storms make moments of high clarity rare. Thus, astronomers who glimpsed what they thought were Martian made waterways often had no chance to confirm their beliefs. The human imagination often leads the eye. A series of unconnected dots can quickly take on a coherent pattern, especially if that pattern is suddenly obliterated by dust or clouds.

Edward Maunder, a British astronomer who was one of many observers to insist that Mars had no canals, decided to test the theory that the so called canals were optical illusions. Inside a group of circles he made a number of irregular, spotlike marks. He lined up some schoolchildren so that they could barely distinguish the spots, and asked them to draw what they saw. All of them connected the spots into straight lines, similar to those that Lowell had put on his maps.

Since the days of Lowell and Orson Welles, the Viking and Mariner space probes have mapped Mars in exquisite detail. We now know for sure that the canals were indeed optical illusions, but Mars does have water frozen as ice. When Viking 1 and Viking 2 landed on the planet, their cameras revealed a bleak and forbidding landscape. No Martians roamed the dry and dusty wastes, but we still can’t prove that the Red Planet has always been lifeless.