The Sirens of Mars

by Sarah Stewart Johnson

  Like most American students, I learned about Euclidian geometry in school, but those lectures and assignments didn’t begin to capture its majesty. The summer I was thirteen, just a few weeks after I’d returned my geometry book to my teacher at Morton Middle School, I drove with my family to eastern Tennessee. My eighty-year-old grandmother was in decline, and my mother was summoned to help. My father couldn’t miss work and needed the car, so he ferried my mother, sister, and me the four hours up and over Jellico Mountain.

  After we pulled into the yard, I opened the car door to the faint smell of submerged vegetation, the slow-moving Tennessee River just half a kilometer away. As I walked to the porch of the small clapboard house, bits of the old weathered smokehouse got stuck in my jellies. The air was thick and hot, the fields overgrown. The coal trains were the only entertainment. When I’d hear one coming, I’d leap up and burst through the screen door, just as my mother and her seven siblings had as children. But aside from when the engines shook the house into a whirl of noise and wind, the summer was shiftless. As the days turned to weeks, my mother realized I needed something to distract me.

  “You like math, don’t you?” she asked one morning as I paced the narrow intersection of the house’s three rooms. She called back to Kentucky and arranged for materials to be mailed to us. Our state university had put together a teach-yourself-by-mail course for its students, designed for freshmen entering with a weak foundation in high school subjects. A few days later, a set of small blue books arrived. “This might be fun,” she said. “Work through the problem sets, then we can walk to the post office and mail them back to Lexington.”

  So that summer, cross-legged on a horsehair couch, I taught myself algebra II and trigonometry. My grandmother, with only a grade school education, looked wide-eyed as I drew and erased conic sections. It hadn’t been my mother’s intention, but the summer of math meant I entered high school ahead of my peers that fall, having already learned arithmetic with polynomials, complex numbers and logarithms, and trigonometric functions. It meant I finished high school math early.

  The fall after I got my driver’s license, I started driving over to the University of Kentucky. I began spending time in the math department, and it was there that I met a professor named Dr. Brennan. He had short white hair and wore his shirts tucked in, his pants high. He had a kind smile, and I’d often see him walking to the pool to swim laps, humming contentedly. He agreed to let me take his number theory course. It was my first foray into pure math, and with it, the world opened.

  The course was essentially Euclid’s Elements, starting with Book 7. But there were no numbers. There was nothing to memorize. There were just words: the posing of problems that at first seemed elementary, easily understood—for example, prove there are infinitely many prime numbers—but the more you thought about them, the more complex they became. Being inside a proof was like being inside a great and turbulent ocean. I would bob about—adrift and confused, struggling to stay afloat. Then there would be a moment when everything would still, the waves would flatten, and I’d see my way to shore.

  I started meeting Dr. Brennan for coffee at seven or eight in the morning, before class began, and we’d work out proofs on the backs of napkins—congruence, divisibility, the building of integers, the construction of perfect numbers. I’d never felt anything more austere and beautiful than when pages of equations would collapse into QED—quod erat demonstrandum, the very thing required to be shown. It was a Kantian ideal, a wondrous kind of knowledge that both existed in the world and was also independent of anybody’s particular experience in that world. It was a complete, self-contained system based not on faith but on reason, and just like so many students before me, I only needed to be shown its inner logic to know it was true.

  Around the turn of the nineteenth century, a mathematician named Carl Friedrich Gauss set out to perfect what he saw as the only potential blemish in The Elements: the fifth of Euclid’s five starting postulates, the fifth of the five things he assumed to be true at the outset and proceeded to use as the basis of his reasoning. The first four were plain as day, like the fact that a straight line could be drawn between any two points. But the fifth, the parallel postulate, was a bit more complicated, a little less self-evident than the others. It hadn’t fully satisfied Euclid either. He’d avoided using it as long as possible, proving the first twenty-eight propositions in Elements without it. When Gauss started tinkering with the consequences of a geometry where Euclid’s fifth postulate didn’t hold, where more than one line could be drawn through a given point parallel to a given line, the results were vexing. He was searching for a contradiction, some sort of logical proof it was impossible, but try as he may, a contradiction never fell out. In fact, he had defined a new type of geometry, and slowly it dawned on him that it was every bit as valid as Euclid’s. He realized that Euclid’s geometry, which seemed so intuitively right, might not hold. Gauss, never one for controversy, kept his doubts a secret until years later, when others slowly came to the same conclusion.

  Neither Gauss nor the geometers who immediately followed, who defined not one but multiple non-Euclidean geometries, lived to see the twentieth century, when the theory of general relativity was published. In it, Einstein posited that stars and planets dimpled the fabric of the cosmos, that space-time was curved and bent by matter and energy. Subsequent deep-space experiments proved him right and, in so doing, showed that Euclid’s fifth postulate, the parallel postulate, didn’t actually describe the physical world. For all its beauty, for all its explanatory power, Elements wasn’t real.

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  I THINK ABOUT this often when I think about the search for life—what we know and what we can trust, what we believe and why we believe it. Deltas are places where we know life to be drawn, sorted, and preserved, where evolution is recorded. We know how to handle a delta. We know where the clays spill out and where to find the bottomset beds. We hope that, like on Earth, they harbor concentrated biological material—quickly deposited and quickly entombed. And Jezero is home to ancient sedimentary rocks that are far better preserved than the most ancient sedimentary rocks on Earth. In all likelihood, the rocks were abandoned quietly and have sat quietly ever since. And yet, as great as this delta is, there are so many other parts of Mars to explore, some just beyond Jezero’s rim.

  Virtually everything we know about the history of life on Earth we know from the sedimentary rock record—from sedimentary stratigraphy—but that’s largely because of the success of photosynthesis, which gave rise to a tremendous proliferation of biological material. As some of it was buried, it imprinted itself like a tattoo onto the skin of our planet. Yet photosynthesis evolved late, well over a billion years into our planet’s history. Before it began on Earth, the simplest, earliest forms of life survived not off the sun but off chemical sources of energy. What if photosynthesis never got going on Mars, or didn’t last? It’s possible that Mars never had a surface biosphere, for by the time photosynthesis evolved here on Earth, Mars was already a pretty hostile place. The planet was bathed in radiation, and the temperatures were frigid, save for the momentary warmth of meteorite impacts. If there wasn’t an extensive surface biosphere harnessing the energy of the sun, then we’re not really sure what we’ll find in a surface delta.

  There are, however, possibilities other than photosynthesis. If life on Mars had a chemical source of energy in the lake, it might have been able to withstand the unforgiving environment. And if it couldn’t, it may well have retreated underground. Here on Earth, the vast majority of microbes are located in the subsurface, stretching their tendrils deep into our planet. We’ve pulled up strange microbial life from some of the deepest subterranean mines in the world, and there are more of those little homes on Mars than on Earth. The rocks are more porous, less compacted from gravity. The science is still new, but we’re starting to understand the kind of life that lives in dark ro
ck, and it’s entirely possible that such life might have existed on Mars.

  It is for this reason that, after completing the primary mission at the delta—a full two years of exploration—the rover will head into the unknown. At least a dozen and a half samples will have been cached, a pile of tubes left on the ground back on the floor of Jezero. The rover will then carry a set of spares off into its new hunting grounds.

  In the distance, some nine hundred sols away, is the edge of Northeast Syrtis, a site called Midway. The landscape at Midway is a little like a Dalí painting. There, giant hunks of terrain were thrust right out of the ground by the Isidis impact. These megabreccia are colossal and beautiful blocks of primordial crust, records of the very earliest days on Mars.

  There are ridges and mesas, hundreds of meters in size, that tower over polygonally fractured terrain. Tucked inside are clays and carbonates but of a different form. The minerals there are most likely to record evidence of subsurface life. We’ll peer into fractures and veins and look for physical interfaces as well as chemical gradients. We’ll search for evidence of exhumed subsurface aquifers. We’ll scour deposits of serpentine, a mineral that forms from hydrothermal activity down in the depths of rocky planets. Maybe there we’ll discover an underground mausoleum, some single-celled version of the catacombs beneath Paris.

  To me, that’s the most exciting part of any mission, venturing into the unknown. There are many risks, of course. The rover might get stuck or caught in a dust storm or simply break. It’s hard to plan for the caching of samples from regions about which we know so little. But if we make it that far, sample return could be an unprecedented catalyst to our effort to understand “life as we know it.”

  Even more intriguing, for me, would be finding life based on new biochemistry. We know how to look for particular classes of molecules, search for recognizable patterns, but those molecules might be different on Mars, and those patterns might not hold. We are still struggling to contend with the truly alien, to recognize and interpret signs of “life as we don’t know it.” But we are making progress. We’re learning how to search for evidence of things like chemical complexity, unexpected accumulations of elements, and signs of energy being transferred, things that could shine a light on life even if it was very different from our own, even if it was built on an entirely different molecular foundation. It’s one of our biggest intellectual and practical challenges—like trying to imagine a color we’ve never seen.

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  IF I’D LIVED and worked in ancient Alexandria, the idea of searching for life elsewhere probably wouldn’t have even occurred to me. Before Euclid was Aristotle, Alexander’s powerful tutor, whose beliefs, like the Elements, hung like a spell over the Western World for nearly two millennia. Aristotle rejected the idea that there was a beginning of the universe or a beginning of time. He rejected the idea of the atom, a thing “uncuttable,” and the atomists who advanced it. The world was not particles and forces. It was not built from inanimate parts. Everything had a fundamental purpose. Objects with fire in them were drawn upward because of their essential nature, just as objects with earth in them were drawn toward the ground. There were some quiescent bits, like rocks, but they too had an essential nature in Aristotle’s view, perhaps one we just hadn’t yet discovered. The heavens—everything above the moon—were pure and perfect. They were a separate realm, made of “quintessence,” and they were wholly apart from human experience.

  Aristotle’s ideas dominated Western thought for centuries, right up until the beginning of the Enlightenment. But, like Euclid’s, many of them were wrong. The Earth wasn’t still, even though no one could feel it moving. Objects of different weights didn’t reach the ground at different times. Flies couldn’t spontaneously generate from meat, nor could eels from mud. The blood of men was not, in fact, hotter than the blood of women, and men didn’t have more teeth.

  The scientific revolution ushered in a penchant for investigation. There were new ideas and new tools. No longer was knowledge a product of the human mind looking inward, of philosophers mulling over the nature of the world. Now it was tested in the laboratory by scientists whose observing eyes and instruments took measure of our world and worlds elsewhere. In rushed marvelous advances—chemistry, gravity, the laws of motion, the basics of medicine—built the same way Euclid’s Elements were built, with one discovery leading to another. Instead of essential natures, we were surrounded by a universe of matter, inhabited by a few inexplicable living things like us. And before we knew it, a paradigm had shifted in our understanding of the cosmos. It was as if a channel avulsed. Like the Great Nile, the sediment built, the water slowed. Before we knew it, the pressure broke, and there was a new path downstream.

  With a mechanical, largely lifeless universe came a newfound existential sorrow. It meant we were potentially alone in the enormity of the now tenebrous night. But the cosmos was obtainable; we could know something about it. In this way, I am a product of my time, a captive of circumstance. I am searching the darkness because there is a universe out there awaiting discovery. It is exciting to live with such possibility, but frustrating to be aware of one’s constraints. William Blake once wrote that “if the doors of perception were cleansed everything would appear to man as it is, Infinite. For man has closed himself up till he sees all things thro’ narrow chinks of his cavern.” That is my experience too, just a few hundred years later. We have human brains within human skulls, and we understand little of what surrounds us. The limits of our perception and knowledge are palpable, especially at the extremes, like when we’re exploring space. There is so little data to tell us who we are and where we are going, why we are here, and why there is something rather than nothing. This is the affliction of being human in a time of science: We spend our lives struggling to understand, when often we will have done well, peering out through those narrow chinks, just to apprehend.

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  THE WORLD THAT Euclid knew—the Alexandria he once strolled—has disappeared. The city was taken by Christians, then Muslims. The lighthouse was destroyed by medieval earthquakes, the last of its remnant stones used to build a citadel. Gone are the mechanical birds that sang from the tops of trees, the steam-powered statues that raised their trumpets to the sky. Gone is the library, which was burned, its shelves emptied. None of it was permanent. It all fell away.

  What parts of us—of all we know, of all we do, of all we are—will escape the same fate? Surely not the rovers, or even those Olympic rings we etched on Mars. Not our current understanding of Mars or its possibilities for life. And, on a planetary timescale, nothing on Earth, for someday the sun will die and swallow it entirely.

  But it is here that I split like a river. By dint of training, experience, and circumstance, I’m with atomists, and a twenty-first-century scientist no less. I know that everything is particles and forces, that we are but a spark of light in a fundamentally inanimate universe. Just as there was a beginning of time, there was a beginning of life. And one day, there will be an end. We are unique and bounded, and we may well be in decline, for we know that species come and go. We are a finite tribe in a temporary world, marching toward our end.

  And what of life itself? Must it be finite as well? What if life is a consequence of energetic systems? What if the nothing-to-something has happened time and again and, because the chinks in our cavern are so small, we don’t know it? For me, this is what the search for life amounts to. It is not just the search for the other, or for companionship. Nor is it just the search for knowledge. It is the search for infinity, the search for evidence that our capacious universe might hold life elsewhere, in a different place or at a different time or in a different form. That confirmation would be a rebuke to the cratered image of Mars, the acid waters, the sterile soil. It would stand in contradistinction to the finite life to which we are confined, to the finite planet we inhabit. Finding life—
even if it is the smallest microbe—would, for me, be the end of akhet. It would be the first dry mound emerging from the limitless dark water. An actual fact about the actual world. A truth, a beginning. It would be a shimmering hope that life might not be an ephemeral thing, even if we are.

  I think of that when I pull out a certain box in my lab. Inside are articles written by Mars scientists who have long since passed away. I return to this collection again and again, with its crinkled pages and old-fashioned fonts, hand-drawn figures and hand-labeled graphs. I’ll pull it down when I’m there by myself, running a script or waiting for an experiment to finish. Even though much of the science these documents postulate is not correct, or at least not entirely correct, in them I can see the great strides forward, the longing for answers.

  It feels like a library of scrolls. The alluvium of my predecessors, the richness of their seeking and striving, all gathered together, and I am trying to plumb it. Next to the articles, there are copies of the riveting letters from William Pickering to his brother and the leather-bound books into which he scrawled his impressions of Mars from the patio beside a plantation house turned observatory in Jamaica. Interleaved are hundreds of pencil sketches and dozens of delicate paintings. There are stills from the silent-film footage of the transatlantic voyage during which Guglielmo Marconi tried to detect signals from Mars: In the laboratory belowdecks, headphones on, he listens intently, somber but determined, his head tilted slightly to the right as the giant aerial spins and spins. There are images of David Peck Todd, including a picture from around 1910 of him standing in an empty field next to his deflated hot-air balloon. He’s wearing a long coat and driving cap and walking toward the camera. The stitched material of his balloon is caught on a tree, and his shadow falls across the collapsing bag. He doesn’t know it then, but over the next fourteen years, as so poignantly captured in the photographs, he’ll try over and over again to run up within shouting distance of Mars. What would he think now that the world is getting quieter? Now that we’re transitioning to fiber-optic cables, now that radio broadcasts may one day cease altogether?