It’s a warm night in mid-October, and I’m winding my way up to the University of Virginia’s McCormick Observatory on a quest to solve an abiding mystery: Why are Earthlings so dang obsessed with Mars?
The observatory’s hilltop dome is open, etching a glowing amber crescent into the autumn darkness. Inside stands a telescope that will help me see Mars as it appeared to observers more than a century ago, when eager astronomers used this instrument in 1877 to confirm the discovery of the two tiny Martian moons, Phobos and Deimos.
Tonight UVA astronomer Ed Murphy has made a special trip up to the observatory, which is closed to the public because of the ongoing coronavirus pandemic. The whirling dance of orbital dynamics has put Mars at its biggest and brightest in the sky right now, and Murphy calculated that this would be the best time to see it from central Virginia, where the turbulent air can sometimes complicate nighttime sky-gazing.
He climbs up a ladder and settles onto the viewing platform, a wooden perch constructed in 1885, and nudges the giant telescope toward the conspicuous orange dot of light. He fiddles with a knob, bringing the planet into focus. “Wait for those few moments when the atmosphere settles down, and you’ll actually see Mars looking crisp and clear … and then it will all get blurry again,” he says through his space-themed face mask.
We swap places. Through the telescope, Mars is an upside-down, peach-pink sphere that swims in and out of resolution. I hesitantly sketch its shadowy features during fleeting moments of clarity, doing my best to channel the 19th-century scholars who once charted its landscapes, some fervently believing that its alien face bore the markings of an advanced civilization.
Today we know there are no immense engineering scars crisscrossing the planet’s vermilion surface. But that doesn’t really matter. Human interest in Mars is ageless. For millennia we’ve made sense of Mars by attaching our deities to it, charting its motion, and mapping its face. We’ve worked Mars into our art, our songs, our literature, our cinema. Since the beginning of the space age, we’ve also hurled more than 50 pieces of hardware—engineering marvels that collectively cost billions of dollars—at Mars. Many, especially early on, have failed. And still our Mars mania marches on.
As I meet with Murphy in October, eight spacecraft are operating in orbit around Mars or exploring its dusty surface. In February 2021, as of press time, three more robotic emissaries are scheduled to rendezvous with the red planet, including a flagship life-seeking NASA rover called Perseverance and two potentially history-making missions from China and the United Arab Emirates.
But, why? Among the worlds we know, Mars is not superlative in any way. It’s not the brightest, the closest, the smallest, or even the easiest to get to. It’s not as mysterious as Venus; not as spectacularly adorned as jewel-toned Jupiter or ringed Saturn. It’s arguably not even the most likely place to find extraterrestrial life—that would be the icy ocean moons of the outer solar system.
“A bunch of red dirt on Mars is not as interesting as some of these other worlds,” says Paul Byrne, a planetary scientist at North Carolina State University. “I don’t advocate for a second that we shouldn’t be exploring it. I do advocate, loudly, that we should be considering how Mars fits into the overall space exploration strategy.”
The scientific reasons why Mars is a compelling target are complex and evolving, propelled by a cornucopia of images and information from all those orbiters, landers, and rovers. Mars is a perpetual enigma, a place we’re always on the cusp of knowing but don’t truly understand. “This is one of the world’s longest unfolding discoveries,” says Kathryn Denning, a York University anthropologist specializing in the human elements of space exploration. “It’s this giant exercise in suspense.”
And the reason Mars remains lodged in the popular zeitgeist might be witheringly simple: Even as our picture of it has sharpened over time, we can still easily envision ourselves there, building a new home beyond the confines of Earth. “It’s just blank enough,” Denning says.
With a sloppy sketch of Mars in my hand, I think of the decades we’ve spent chasing little green men, and microbes, and human settlements, and how Mars fervor has returned after every setback. At the same time, I know plenty of scientists are ready to heap our dreams—and our robots—onto other inviting destinations across the solar system. As scientists juggle limited resources and increasing competition, I can’t help but wonder if we’ll ever shake ourselves loose from the allure of Mars.
Since civilizations first gazed skyward, humans have followed Mars and charted its capricious path through the heavens. As the Sumerians tracked this “wandering star” crossing the sky in the third millennium B.C.E., they noted its foreboding color and associated it with the malevolent deity Nergal, god of pestilence and war. Its movements and varying brightness portended the deaths of kings and horses or the fates of crops and battles.
Aboriginal cultures also note its color, describing it as something that has been burned in flames or linking it to Kogolongo, the native red-tailed black cockatoo. The pre-Columbian Maya carefully plotted the object’s position relative to the stars, tying its movements to shifting terrestrial seasons. The Greeks associated it with Ares, after their god of war, whom the Romans recast as Mars.
“There was always only one actual planet Mars, but there are a lot of different cultural Marses in play,” Denning says.
By the mid-1800s, telescopes had transformed Mars from a mythological figure into a world. As it came into focus, Mars became a planet with weather, shifting terrains, and ice caps like Earth’s. “The very first time we had a way to look at Mars through the eyepiece, we started discovering things that were changing,” says the SETI Institute’s Nathalie Cabrol, who has studied Mars for decades. With more advanced instruments, this dynamic place could be studied—and mapped.
During the Victorian era, astronomers sketched the Martian surface and presented their drawings as fact, although the whims and biases of the mapmakers influenced their final products. In 1877 one of those maps captured international attention. As drawn by the Italian astronomer Giovanni Schiaparelli, Mars had harshly delineated topography, with islands that erupted from dozens of canals, which he colored blue. Schiaparelli stuffed his map with detail, and instead of conforming to contemporary naming conventions, he labeled the exotic features on his version of the planet after places in Mediterranean mythologies.
“That was a really massively bold statement to make,” says Maria Lane, a historical geographer at the University of New Mexico. “It’s basically him saying, I saw so much stuff that was so different from what anyone else had seen, I can’t even use the same names.”
As a result, Lane says, Schiaparelli’s map was instantly authoritative. Scientific and popular opinion pronounced it a powerful representation of truth. Three decades of unconstrained Mars mania followed, and by the end, any reasonable person would be forgiven for believing intelligent Martians had built a planet-spanning network of canals. Much of that fervor can be linked directly to Percival Lowell, a quirky aristocrat with a serious Mars obsession.
A wealthy Bostonian and Harvard University alum, Lowell had more than a passing interest in astronomy, and he was an avid reader of scientific and popular texts. Inspired in part by Schiaparelli’s maps, and believing that alien technology had crafted the Martian canals, Lowell raced to build a hilltop observatory before the autumn of 1894, when Mars would make a close approach to Earth and its fully sunlit face would be prime for observing those supposed canals.
With the help of some friends and his family fortune, the Lowell Observatory emerged that year near Flagstaff, Arizona, on a steep bluff that the locals named Mars Hill. From there, among the conifers, he dutifully studied the red planet, waiting night after night for the shimmering world to come into focus. Based on his observations and sketches, Lowell not only thought he could confirm Schiaparelli’s maps, he believed he spotted an additional 116 canals. “The more you look through the eyepiece, the more you’re going to start seeing straight lines,” Cabrol says. “Because this is what the human brain does.”
In Lowell’s estimation, the Martian canal builders were supremely intelligent beings capable of planetary-scale engineering—an alien race intent on surviving a devastating change in climate that forced them to build mammoth irrigation canals stretching from the poles to the equator. Lowell published his observations prodigiously, and his conviction was infectious. Even Nikola Tesla, the electric pioneer who famously sparred with rival inventor Thomas Edison, got caught up in the moment and reported detecting radio signals coming from Mars in the early 1900s.
But Lowell’s story began to fall apart in 1907, in part because of a project he funded. That year, astronomers took thousands of photos of Mars through a telescope and shared them with the world. Planetary photography eventually replaced cartography as “truth,” Lane says. Once people could see for themselves how the photos and maps of Mars didn’t match, they no longer bought into the authority of Lowell’s maps.
Still, by the turn of the 20th century, Mars had become a familiar neighbor with changing landscapes and the lingering promise of inhabitants. The next wave of observations revealed that seasonally, the Martian polar caps shrank and expanded, unleashing a swath of darkness that crawled toward the equator. Some scientists in the 1950s thought those shadowy areas had to be vegetation that flourished and died back, theories that made it into top-tier journals. All this scientific fervor fueled a trove of speculative fiction, from H.G. Wells’s War of the Worlds and Edgar Rice Burroughs’s Barsoom serials to Ray Bradbury’s Martian Chronicles.
“In the days before we’d really explored Mars, pre-1960s, there was just a wealth of imagination,” says Andy Weir, author of The Martian. “A science fiction author could say, I don’t know anything about Mars, so I can say whatever I want about Mars.”
Then, in 1965, NASA’s Mariner 4 probe swept by the red planet. It captured the first close-up images of the Martian surface in black and white, transforming the rich pop culture playground into a grainy, cratered landscape. Seen at last, the planet’s arid sterility was a stark disappointment. But it didn’t take long for the idea of life on Mars to rekindle in human imaginations.
In a sense, the isolation of the COVID-19 pandemic has given me a feel for what workdays must be like for Mars scientists. I usually travel extensively, getting my notebooks dirty as I chase stories across deserts, sweltering jungles, and sea ice. Currently, Mars explorers spend their lives trying to understand a place that will come into focus only through a lens or on a computer screen. They won’t soon plunge a glove into its alien soil or brush dust from their visored faces; remotely guided rovers must do the work instead.
On a Tuesday morning in October, I’ve turned on videoconferencing to talk to the SETI Institute’s Cabrol, who is across the continent in California. Instead of a bookshelf, artfully arranged, she has a vision of Mars as her backdrop. It’s an expansive vista, with dark, boulder-strewn peaks straddling rusty plains and distant ridgelines in the orange haze. That’s fitting, I think, for a scientist who’s spent decades immersing herself indirectly in Martian landscapes.
Then Cabrol shifts. Tire treads, trucks, and a cluster of bright orange tents appear in the foreground. Instead of staring at Mars, I’m seeing an image of one of Cabrol’s field sites in the Chilean Altiplano. For decades she has scoured this high desert for Mars-like environments, looking for life on volcanic peaks and in high lakes and trying to imagine how a robotic avatar might accomplish the same task, tens of millions of miles away.
Cabrol and other modern scientists focused on Mars owe a debt to Mariner 9, the first spacecraft to orbit Mars in 1971. At first, Mariner couldn’t see through a massive planetwide dust storm. “Mars was still trying, until the last minute, to keep a veil of mystery,” Cabrol says. But as the sand settled, the camera spied the summits of the humongous Tharsis Montes, a trio of volcanoes dwarfed only by neighboring Olympus Mons. To the east was mammoth Valles Marineris, a rift valley that resembles Arizona’s Grand Canyon, only nine times longer.
Most importantly, in the thousands of photographs taken by Mariner 9, scientists saw ancient river-carved valleys, floodplains, channels, and deltas. They also picked up chemical clues of water ice. These were all signs that flowing water once sculpted exotic Martian landscapes.
“The geologic evidence is overwhelming that the climate was very different than it is today,” says Ramses Ramirez, who studies the ancient Martian climate at the Earth-Life Science Institute in Tokyo, Japan. That realization changed the course of Mars exploration. “It was so much more profound than all the folklore we could have in mind,” Cabrol says, “and another adventure started. The scientific one.”
Knowing that ancient Mars may have been a somewhat Earthlike abode ignited a new set of questions in planetary evolution, and it reinvigorated interest in finding out whether life may have once existed on Mars or, with luck, still did. “I think it’s fascinating that we’re still dealing with the same themes as Percival Lowell would recognize,” says Rich Zurek, chief scientist of the Mars Program Office at NASA’s Jet Propulsion Laboratory (JPL). “Just ... no canals.”
NASA quickly followed Mariner 9 with an even more ambitious mission. In 1976 humans finally were able to gaze at the red planet from eye level when the twin Viking landers touched down in the northern hemisphere. By that time, scientists already knew vegetation didn’t seasonally carpet Mars; those shifting shadows were the work of dust storms whipping up volcanic sand. They also already knew that water didn’t flow abundantly over its surface anymore.
But they didn’t know whether the planet’s soils were devoid of life, and at least one astronomer—Carl Sagan—wasn’t ready to completely abandon the idea of even larger life-forms.
Just in case Martians were nocturnal, “for a long time, we had a very high-intensity lamp planned to be on Viking so that we could take pictures at night,” recalls Gentry Lee, a science fiction author and chief engineer at JPL. To Sagan’s disappointment, the Viking team decided to remove the lamp from both landers, and if you had pressed Sagan about whether he truly expected to see Martians wandering by he’d probably demur, Lee says.
The Viking experiments found no Martian microbes and no footprints in the sand. Instead, they unveiled hints of perchlorates in the soil, compounds that can destroy organic molecules and potentially erase any traces of carbon-based life. “So, you couldn’t even look for the bodies, if you will,” Zurek says.
But Viking did send back images of ruddy, rock-strewn plains that looked like they could have been snapped from any arid place on Earth. New views of Mars kept flooding in, as NASA landed rover after rover on the planet’s desolate surface: Pathfinder in 1997, then the twin Spirit and Opportunity rovers in 2004, followed by the Curiosity rover in 2012. Each vehicle arrived outfitted with increasingly sophisticated cameras, and together they sent back roughly 700,000 images. Now when we see those rover tracks in the soil or we see the robot selfies showing them perched on a colorful crater rim, we can more easily imagine ourselves in their treads.
“Once you land, there’s this whole evocation of what it means to be a human in this place,” says Yale University anthropologist Lisa Messeri, who studies how space-based imagery affects our perception of worlds.
About an eight-hour drive from Istanbul, Lake Salda in southwest Turkey is a local haven. Dark volcanic rocks tumble toward the brilliant white sandy beach ringing the shore. Clear aquamarine waters become a deep abyssal blue near the lake’s center, where the bottom is hundreds of feet down. It’s an almost perfect modern analog for Jezero crater, the spot where NASA’s Perseverance rover is targeting its search for signs of ancient life.
“The locals call it the Maldives of Turkey,” says Brad Garczynski, a graduate student in planetary science at Purdue University who traveled to the site in 2019. “You could imagine yourself as a little microbe tanning yourself on the shoreline of Jezero.”
It’s dry now, but the sculpted terrain suggests that Jezero once was filled with a deep, large crater lake fed by flowing rivers. More than 3.5 billion years ago, water likely rushed into Jezero from the north and west, depositing layers of sediments in fanning deltas near the crater walls. Over time, the crater filled and flooded, eventually sending water back out through a breach to the east.
From orbit, spacecraft have identified clays and carbonate minerals near Jezero’s deltas that require water to form. Lake Salda’s white sands similarly are made of busted-up carbonates called microbialites, rocky structures made when dissolved carbon dioxide forms carbonate ions that react with other elements, such as magnesium, and precipitate rapidly, trapping organic compounds. On Earth this process forms layered structures that preserve the oldest evidence of terrestrial microbial life, dating back 3.5 billion years. Scientists are hoping that Jezero’s carbonates did the same, and that they trapped anything that once inhabited the lake or its ancient shores.
“It’s one of the reasons we’re excited about Jezero crater,” says Purdue University planetary scientist Briony Horgan. It’s also why Garczynski is practicing being a Mars rover in Turkey: He’s looking for the most likely places for biosignatures to be preserved, and he’s figuring out what they’d look like to Perseverance. To do that, he collected nearly a hundred pounds of samples from Lake Salda and flew them home in a suitcase.
Like Garczynski, Perseverance will be collecting rocks for a return trip, although maybe just 450 grams, at most. As the rover wheels around Jezero, its onboard cameras—which see Mars in multiple wavelengths—will help it identify the most tantalizing rocks to collect. The rover will cache those samples and leave them on Mars, where they’ll wait for a ride home on a future spacecraft. Once they arrive in Earth-based laboratories, scientists will use the best possible instruments to read the record of Mars’s ancient climate and tease out any possible signs of life.
Or maybe, with luck, Perseverance’s advanced cameras will be the first to glimpse evidence of fossilized Martians.
If anything, though, Mars has taught humankind that we often fall prey to wishful thinking about life on its surface. From canals to vegetation to hotly debated hints of fossils in Mars meteorites, the red planet repeatedly has paved over our hopes with bleak, barren realities. So why, then, are we sending yet another spacecraft to look for life on Mars—not even for organisms that are alive today but for traces of organisms that may have flourished billions of years ago?
“We. Haven’t. Looked. For. Life. On. Mars,” Cabrol asserts, getting animated. “If you don’t have a good understanding of the environment, how are you going to be able to decrypt or extract a life signal out of that?!” Even Viking, she says, which was purportedly a life-finding mission, carried an experiment that was designed without enough knowledge of the Martian environment to reasonably succeed.
But those ancient landscapes are still there, preserving a record of the planet’s infancy and a time when life could have thrived in a slightly wetter period, blanketed by a thicker atmosphere.
“We know the canals don’t exist, we know there is no pyramid on Mars, no alien civilization, no Tupperware,” Cabrol says. But if we do find that some prebiotic chemistry littered the Martian surface, we may learn something about how life evolves on any rocky shores—including our own.
What if Perseverance finds no evidence for Martian fossils or even signs that places like Jezero could have been inhabited? Will we ever be able to give up on the idea of life on Mars? Probably not, admits David Grinspoon, senior scientist at the Planetary Science Institute. “It’s very hard to kill the idea that Mars is somehow hiding life from us,” he says. “It’s very, very tenacious.”
In a way, that stubbornness is perhaps the most blatant manifestation of our desire for companionship, a longing for communion, a need to know that we are not alone in the universe. Humans, for the most part, need other humans to survive, and maybe that’s true on a planetary scale as well.
“We are not a solitary people,” Weir says. “At a macroscopic level, we—humanity—we don’t want to be alone.”