Steve
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Canals of Mars

Discovery

In 1877, Giovanni Schiaparelli of Italy was looking at Mars through his telescope and saw what he described as canali.  I cannot speak Italian, and would probably guess that this meant canals.  This is what many English speaking people did at the time, but apparently it means channels, not specifically canals.

Percival Lowell

This meant that people looking at Mars tried to make out the network of canals.  The most famous of those who succeeded was Percival Lowell.  He was looking at Mars from Arizona. Mr. Lowell made maps of the canals.  Not everyone could even see them, but some other astronomers confirmed the observations.  In some cases, people who had not seen Mr. Lowell’s maps drew ones of their own with definite similarities to his.

It was realised that for the canals to be seen from the Earth, they would have to be huge.  This was engineering on a vast scale, bringing water from the poles of Mars to the warmer equator where the water could be used for irrigation.

  Alfred Wallace

Not everyone was convinced.  Alfred Wallace was a multi talented man.  He was the co-proposer of the theory of evolution by natural selection with Charles Darwin in 1859.  He also researched the border between predominately Asian animals and mainly Australasian ones.  This line is called the Wallace Line.

Mr Wallace did calculations based on the knowledge of the time of the conditions on Mars.  His conclusion was that all the water would have evaporated long before reaching the equator of the planet, and far from being the work of highly intelligent engineers; if the canals existed it would have been a work of insanity.

Micro-organisms

Mr. Wallace was excluding the possibility of canal building engineers, but was not commenting on the possibility of micro-organisms on Mars.

Mars Probes

The first successful flyby of Mars was in 1964 by Mariner 4, and the first successful orbiting of Mars (or of any planet other than Earth) was by Mariner 9 in 1971. These and other missions sent back much more detailed pictures of the Martian surface than had been obtained from the Earth, and there were no canals in the pictures.

How did it happen

For nearly a century, many astronomers had been reporting non-existent canals on Mars. One theory about this is that they had been connecting up unrelated features into an apparent network.  The trouble with this theory is that the Mars missions do not show features than could have been mistakenly joined together on the maps.

My Explanation

The Human Brain is very good at seeing patterns, and we frequently see patterns that are not even there.  This applies to numbers as well as pictures.  If you give an untutored person a group of random numbers, they will often be able to see patterns in them.

The Astronomers, even the ones who had not seen Mr.Lowell’s maps, knew that there was a network of canals taking water from the poles to the equator, so they looked until they found it.  The similarity to other people’s maps is probably just that these were logical places for canals.






The Canals of Mars
as seen by Percival Lowell

 
 
 Giovanni Schiaparelli's map of Mars, 1888
 
 
 
Below and to the left of Acidalia are the massive Martian canyon systems of Valles Marineris, some of which form long linear markings that were once thought by some to be canals.
By NASA, Steve Lee University of Colorado, Jim Bell Cornell University, (Great Images in NASA Description)[see page for license], via Wikimedia Commons
Picture was taken with the Hubble Space Telescope in 1999.