 The year is 1877. Your name is Giovanni Schiaparelli, and you're looking up at the night sky. Recent advancements in telescopes allow you to peer deeper into the heavens than ever before. Over the length of your career, you'd come to push mankind's knowledge of binary stars, discover asteroids, and realize the relation between meteor showers and comets. But above all that, your observations tonight would come to define your legacy. Although the telescope had been invented more than 200 years prior, modern astronomy was still in its infancy. Much was still unknown about the workings of the heavens after the fall of the Potomac view of the solar system, with Earth at its center. Giants such as Galileo, Newton, and Kepler had laid the foundations, but you knew much was yet to be discovered. As you gaze upon the marvels of the heavens, you come across the red titan, Mars, named after the mythic Roman god of war. As one of the five planets visible to the naked eye, Mars had been known about since antiquity, but tonight, you notice something different. With the aid of a state-of-the-art telescope, you notice a dense network of linear structures across the surface of the red planet. In your notes, you begin to make the first in a series of detailed drawings about the dark lions covering the Martian surface. You call them canale, meaning channels in your Italian tongue, referring to the shape of the lions. You don't know it yet, but these canale would go on to spark one of the greatest astronomical debates of the 20th century, but they would prove to be an optical illusion, a stargazer's mind playing tricks on them in the night. In 1878, after months of detailed observations, you publish your findings, setting the stage for what was yet to come. It didn't matter that nobody else at the time saw your neat, regimented lions, many others would come to see them too. Instead of its proper translation of channel inferring nothing about the lion's origins, it's mistranslated to canal, by definition, man-made, or in this case, Martian-made. These findings caught the eye of Percival Lowell, an American astronomer determined to make a name for himself in the astronomical world. Lowell read about Scapparelli's work, and he set out to study the canals of Mars and uncover their true purpose. In 1894, he built a new observatory in Flagstaff, Arizona. Coincidentally, the same observatory that just a few decades later would uncover small, icy rock at the edge of our solar system, Pluto. But now, for the next 15 years, he studied Mars extensively and made intricate drawings of the surface markings as he perceived them. Lowell published his views in a series of three books. With these writings, Lowell, more than anyone else, popularized the belief that these markings show that Mars sustained intelligent life. In his books, Lowell put forth a theory that the canals were visible traces of a dwindling civilization's attempt to tap the planet's polar ice caps. This idea wasn't too far-fetched. The late 19th century was a period of great canal building on the home planet. The Suez and Panama canals were both freshly dug at the end of the 1800s, and so the dreamy hypothesis that Scapparelli's canali were irrigation canals made by intelligent beings resonated in the minds of the people. About his research, Lowell would go on to say that Mars is inhabited by beings of some sort of other we may consider as certain as it is uncertain what those beings may be. Although Scapparelli was more restrained in his writings on the origin and use of his canali. In his book, Life on Mars, Scapparelli wrote, rather than true channels in a form familiar to us, we must imagine depressions in the soil that are not very deep, extended in a straight direction for thousands of miles, over a width of 100, 200 kilometers, and maybe more. I have already pointed out that, in the absence of rain on Mars, these channels are probably the main mechanism by which the water and with it organic life can spread on the dry surface of the planet. Scapparelli and Lowell weren't alone in their observations. Many astronomers seconded Scapparelli's initial observations. The Irish astronomer Charles E. Burden and the Danish astronomer John Dreyer both published their sketches of the Martian lines in the fourth edition of Celestial Objects, a prominent astronomical edition of the time. But the consensus was far from unanimous. Edward Mondaire at the Royal Observatory in London began challenging the prevailing narrative. He conducted visual experiments using circular disks marked with small discrete black dots. This led him to conclude correctly that viewing of the canals arose as an optical illusion. Mondaire was also convinced that there could not be life, as in our world, on Mars, as there were no temperature-equating winds and too low mean temperatures. Over time, the consensus started to shift. In 1909, French astronomer Eugene Antoniadi, who had long supported Lowell's belief, began observing Mars at the Moudin Observatory in Paris, the largest telescope in all of Europe. What he saw too began to challenge Lowell's 15 years of canal mania. By 1910, new photographic techniques began further questioning the existence of such canals. Coincidentally, Scapparelli died in 1910. Lowell's obituary for him would be the last time he actively defended the dream of Martian canals. With Scapparelli's death and Lowell's end to the canal mania, the belief in the canals began to subside from public conscious. Although papers and scientific publications would continue to debate the subject for decades, the final nail in the coffin came with the arrival of Mariner IV in 1965, which took high-resolution images of the Martian surface, revealing impact craters, large mountains, but a complete absence of canals. The scientific hysteria behind the Martian men died down, believed on in science fiction and movies, depicting Martian civilizations coming to Earth to take our bountiful resources. Today, the most common belief as to the cause of the canali supports Edward Mondaire's belief that it was an optical illusion created by the mind seeing lines between the dark craters scattering the Martian surface in the fuzzy images of their telescopes. You can see this for yourself by staring at a collection of black dots and seeing a series of dark lines begin to connect them. Still, others have suggested, based on Lowell reporting a near-identical canal system on Venus that he and others like him may have been observing the projections of their veins and their eyes on the surface of the planets, a known nuisance among planetary observers using high magnification. However, recent discoveries may shed even more light on this century-old conundrum. This past August, scientists found dozens of mountains across the southern hemisphere of Mars where previously undetected dark streaks come and go with the seasons. When the planet heats up, the streaks appear and expand downhill, then disappear when it gets cold, which may be evidence of salty water running down slopes during the Martian summer. Although we may never know, perhaps this played a role in Schiapparelli and Lowell's observations. Although Schiapparelli had a long and storied career studying the cosmos and never officially supported the idea that his findings proved the existence of intelligent life on Mars had ended up becoming his largest legacy and what he is most remembered for today, all because of a mistranslation. This was the first in a series of scientific stories I plan on telling, explaining how important breakthroughs and misconceptions came to be. If you know any stories you want told, be sure to leave them in the comment section below. And if you enjoyed the episode, consider subscribing. And remember, there is always more to learn.