For this week’s Fault Lines column, Jon Allsop is filling in for Jay Caspian Kang.

In 1877, Giovanni Schiaparelli, an Italian astronomer (and uncle of the fashion icon Elsa), started making a map of the surface of Mars, which was then at one of the closest points to Earth in its orbit. Schiaparelli was color-blind, but this affliction may have increased his ability to see geometric outlines, and what he observed on Mars was extraordinary: not only shapes that resembled oceans but long, straight lines between them. The lines were mysterious—“They may disappear wholly, or be nebulous or indistinct, or be so strongly marked as a pen line,” Schiaparelli observed—and would sometimes even double up. Schiaparelli wasn’t sure what they represented, but he dubbed them “channels,” or, in Italian, canali. In the Anglophone world, they soon became “canals.”

About fifteen years later, a Boston Brahmin named Percival Lowell fell under the spell of Schiaparelli’s “canals.” Born in 1855, Lowell had spent his twenties and thirties touring Japan and Korea, which had just opened up to the West, and writing about his experiences, but in the eighteen-nineties he turned his attention—and considerable means—toward the cosmos. Lowell was an amateur, but he hired two Harvard-affiliated astronomers who knew what they were doing, founded a namesake observatory in Arizona, acquired top-notch equipment, and began observing Mars for himself. In 1895, he would assert, in a series of lectures, that the lines on the planet’s surface were proof of a highly sophisticated irrigation system, feeding oases where the inhabitants of Mars would tend crops to survive an otherwise hostile environment; the system was suggestive of “a mind of no mean order,” Lowell said, one of “considerably more comprehensiveness than that which presides over the various departments of our own public works.” Lowell made his case with such “seeming logic” and “disarming humility,” the journalist David Baron writes in his new book, “The Martians: The True Story of an Alien Craze That Captured Turn-of-the-Century America,” that, if Baron had attended Lowell’s lectures, he could imagine himself having been “swept along.”

In the initial years after Schiaparelli observed his canals, no one credible believed that they were of intelligent design, despite some chatter to that effect in the press. (As Baron notes, the word “Martians” was not even in common usage yet, with reports instead referring inconsistently to “Marsians,” “Marsonians,” “Marsites,” or “Martials.”) Lowell’s lectures, reproduced in The Atlantic Monthly and in book form, began to sell the public on the idea, and, as American popular culture started to become more unified, Mars—and Martians—became a meme, popping up everywhere from advertisements to vaudeville. “The War of the Worlds,” H. G. Wells’s terrifying tale of a Martian invasion of London, found an audience in the U.S., and the engineer Nikola Tesla claimed to have detected a signal from Martians trying to contact Earth. The sensationalist yellow press, at the peak of its influence at the time, lapped it all up.

Even at this point, the idea of life on Mars wasn’t taken seriously by everyone; more sober observers still saw it as entertainment at best, nonsense at worst. (When the Chicago Tribune reported on Tesla’s claim, they included suggestions from “one or two who know him” that, in passing electric current through his body, the inventor had fried his brain.) But over time, as Lowell and his associates offered more supposed evidence of the irrigation system, the theory gained widespread credibility: the conservative New York Times, which had initially been standoffish toward Lowell, eventually profiled him under the headline “THERE IS LIFE ON THE PLANET MARS”; by 1907, a Wall Street Journal editorial was talking of “proof” of “conscious, intelligent human life.” This was not a hoax, exactly; Baron makes a convincing case that Lowell believed passionately in his grandiose claims, and that many members of the public wanted to believe in them, at a time of disorienting change. Eventually, however, Lowell’s ideas were discredited—Schiaparelli, once an ally, renounced them—and the world moved on. To the end, Lowell refused to abandon his belief. He fumed, at one point, that the problem wasn’t a lack of intelligence on Mars, but on Earth.

Today, it’s hard to mentally disentangle talk of mass delusion from the supercharging force of the internet. But a paranoid vein has always run through American public life, as I wrote in a column on the recent Jeffrey Epstein panic. In chronicling Lowell’s story, Baron deftly shows how fantastical beliefs gained purchase in a pre-Facebook age, not only thanks to print media but through social institutions such as churches and women’s clubs. Baron likens the Mars craze to a “burgeoning wildfire.” His book actually shows an outlandish idea metastasizing more slowly than that, gaining credibility and respectability over a period of a decade or more. But, even in our current age of instantaneous information exchange, this dynamic remains highly recognizable. (Exhibit A, as I have contended elsewhere, might be the Epstein panic, which has eaten its way from the conspiratorial fringes to become a serious matter for the mainstream press.) So, too, does the sense of epistemological confusion that Baron describes as pervading the period, one in which it was difficult to “separate insight from delusion, to identify who were the geniuses and who were the cranks.”

Still, if Baron deftly illustrates the historical roots of collective phantasms, his book is ultimately most interesting for what it says about the timelessness of our shared fascination with the stars, and Mars in particular. Paranoia-inducing fictions like Wells’s aside, the public came to view Martians not as monsters but as representatives of a higher civilization—as angels, even, at a time when new science was shaking old religious certainties. If the tale of Lowell and his quest can be read as a warning against mass delusion, Baron writes, it is, ultimately, a love story. To some extent, it seems to have seduced the author himself. Baron persuasively argues that giving in to our imaginations might not be the worst thing—even if today, amid what future historians might dissect as a second Mars craze, pinpointing the blurred lines between truth and fiction can feel like a more urgent task than ever, and geniuses often turn out also to be cranks.

If one were to compare Elon Musk to a character from Baron’s book, then Nikola Tesla, the mad inventor, might seem the most obvious candidate; Musk, of course, named his car company after Tesla, and has called him “one of the greatest engineers ever.” But there is more than a touch of Lowell about Musk. Musk, too, is a very rich person with a long-standing Mars obsession; his dream of facilitating human life on the planet—which he has styled as “life insurance” for humanity in the event of disaster on Earth, and likened to backing up a hard drive—is the guiding mission behind not only his rocket company, SpaceX, but, to some extent, his other businesses, too. Unlike Lowell, Musk doesn’t appear to believe in intelligent life from Mars—indeed, he suggested to GQ, in 2015, that he saw its absence as a sort of ethical permission slip for human colonization. But, in the same interview, he did use the word “Martian” to describe humans who might move there. Lowell once wrote that he was “half-Martian,” albeit jokingly. (He was born on a Tuesday in March—or, in French, a mardi in mars.) Musk has said that he hopes to die a Martian, by his definition, albeit not “on impact.”

The decade-old GQ interview—in which the “endearingly boyish and geeky” Musk was credited with making outlandish ideas sound “not only sane, but sensible”—and articles like it bestowed a certain credibility on his Mars designs. He, and they, have since gained political traction. After endorsing Donald Trump in last year’s Presidential election, Musk danced around at a rally wearing a T-shirt that read “OCCUPY MARS”; once Trump won, he tapped Musk to lead the (supposedly) cost-slashing Department of Government Efficiency, and the shirt reappeared in the Oval Office; in between, Trump pledged, at his Inauguration, that the U.S. would “plant the Stars and Stripes” on the planet. Behind the scenes, Musk appeared to be reshaping U.S. space policy, which had otherwise recently prioritized a return to the moon over putting humans on Mars, a goal that Musk appeared to dismiss as a distraction. Since then, of course, Trump and Musk’s relationship has blown up, and the moon-first path again seems locked in. SpaceX, however, has continued apace with its Mars projects, which, the Times reported last year, may now involve designing Martian homes and exploring the potential for procreation there. (According to the Times, Musk offered up his sperm to seed a colony; Musk denied this and other aspects of the story.) This week, after several failures, the starship that SpaceX wants to send to Mars conducted a successful test. (The ship is also slated for use by NASA in its moon mission; Sean Duffy, NASA’s acting administrator, hailed the test as a “great day” for the agency. You can take Musk out of the government, but not the government out of Musk.)

Baron, showing admirable restraint, doesn’t name Musk in his book, though he does refer to him as a “conspicuous tech billionaire” in a passage about the modern-day hopes of making Mars habitable. Baron acknowledges that such hopes might one day be viewed as Lowellian naïveté. But he doesn’t dismiss them. In a recent interview with Space.com, he said more explicitly that he is “very excited” by Musk’s ideas, even if achieving them will be “so much harder than we can possibly imagine.” And he referred back to the conclusion of “The Martians,” which explores how, though the Lowell-era Mars craze was rooted in delusion, it helped inspire the subsequent space age, which would enhance our understanding of the planet. Baron’s book “set out to tell a story of human folly,” he writes. “That is, of course, one lesson of the tale, but I discovered another, perhaps more powerful takeaway: Human imagination is a force so potent that it can change what is true.”

This is a noble insight, at a time when mass delusion has an understandably bad rap. It got me wondering whether Musk and his ilk might one day be seen in such a charitable light. That’s impossible to know, of course, as is the feasibility of one day getting humanity to Mars, never mind setting up a colony. (As a layman, I’m open-minded—though the scientific obstacles strike me as many and enormous, and Musk’s time horizons, which at one recent point foresaw crewed missions as soon as 2028, strike me as preposterous.) Still, there’s no question that scientific progress relies on trial and error and attempting to achieve the improbable.

In many ways, though, Baron’s depiction of Lowell’s age makes for a pessimistic contrast with our own. Sure, it was, like ours, turbulent, often violent, and swimming in noxious ideas. But it was also an era of what Baron describes as “giddy optimism” and “limitless possibility.” Our age, too, is one of rapid technological advancement. But not everyone has seen adequate progress in this; a famous maxim associated with the tech billionaire Peter Thiel, for example, complains that “we wanted flying cars” but instead “got 140 characters,” a reference to the ubiquity, and comparative mundanity, of social media (and, specifically, Twitter, which Musk now owns). It is certainly hard to see this as a time for optimism. Knowledge-wise, science may be advancing, but, politically, its powers of persuasion are in retreat, in a moment defined, in many ways, by ignorance and narrow-minded grievance. One of the main avatars of this trend has been Musk, who has recently been discredited in the eyes of many, not for anything he said about Mars but for his Earthly behavior as a culture-war crusader and a hatchet man for Trump. (That is, until he suggested that Trump is in the Epstein files.) In June, Thiel suggested to the Times that Musk has given up on Mars, at least as an all-consuming political goal, after concluding that socialism and wokeness risked following humanity there, meaning that the priority had to be stopping those values on Earth first.