Martial canals are mysterious straight lines along the equitorial regions in Mars.

The planet Mars has always fascinated humanity. In fact, it seems to interest us considerably more than most things in the night sky.

This makes sense; Mars is often not only clearly visible but conspicuously red like blood. So many ancient societies associated Mars with war, always of considerable interest to the human species. Mars appeals to us both as a physical object for observation and as a lure for mythological speculation.

There is a duality here. On the one hand, there is the visible planet; the red coloration reflects its geology. On the other hand, there is the Mars of interpretation, whose red color reflects its attributional warlike nature; this says a lot more about human psychology than it does about the planet Mars itself.

The red planet causes us to observe and to speculate.

Speculation. That’s where the problems come in. There is physical reality, and there is interpretation; and it is frequently the interpretation, rather than the reality, that seizes the attention of human beings. Our brains are remarkably predisposed to the interpretation of objective physical reality in psychological, self-referential terms. Unfortunately, these terms are frequently just plain wrong. So, maritan canals do not exist.

https://www.theatlantic.com/magazine/archive/1895/08/mars-part-iv/309151/