By Gregory L. Vogt
By Kevin Nolan
By Andrew Chaikin
Imagine the scenario:
You’re a hardy crew, but even so, it’s been a long trip. You boarded your cryogenic sleeper-ship in orbit of your home world circling Proxima Centauri decades ago, a hundred of you in the chemical-bath berths of your vessel, specialists and technicians committed to the search for a new world. Once your ship escapes Proxima’s gravity well, its tachyon ramjet begins accelerating your vessel toward a small fraction of lightspeed, which, once reached, you maintain for five or six minutes (all you have fuel for), and now, years later, your long coasting has brought you at last to the sensor-outskirts of the only star system within feasible reach of your technology. Your long-range telescopes have only been able to tell you so much – you had to come and see for yourself. As your craft draws near that system, the chemical-baths disgorge the whole crew, all eager at the approach to your last chance, the repository of all your hopes for survival.
And you’re horrified.
You’re horrified because before you can even reach the solar system of your long desire, you encounter the Kuiper Belt – a swarming field of millions of caroming comets and hurtling chunks of rock. Suddenly your ship’s somnolent navigational computers must leap and lunge simply to prevent your hull from being sieved by a thousand random collisions. It’s a pointed solar “Keep Out” sign, and only the fact that your interstellar voyage isn’t equipped to ever return you to your home world keeps you from turning back. Somehow, you make it through, even managing to dodge the biggest and last of the Kuiper objects, the lonely planetoid Pluto. The solar system lies before you, with Sol, its star, a distant pin-prick in the canvas of black.
First you encounter Neptune, a dark blue ball of hydrogen and helium several hundred times bigger than your home world, a frightening gas giant with storms so violent their winds are supersonic, and with what life-sustaining elements there are (water, oxygen, etc) trapped forever in a thousand miles of maelstrom forever howling around a compacted core of crushed solids. The planet is throwing off plenty of its own heat, but none of its retinue of moons receives enough heat or light to welcome visitors.
Next is Uranus, even larger than Neptune, another darkly glowing mass of ferocious winds followed around in its orbit by a swath of inhospitable moons. You’ve long known that this is often the way with outer planets (your own system has three much like these two), but still, you had hopes that some of the moons would have bits of atmosphere, tiny shreds of welcome. But no.
Your disappointment is mounting, but it’s momentarily lightened by the awesome spectacle that greets you next: the enormous planet Saturn, far larger than any planet you’ve ever encountered, a luminously beautiful sight haloed by a gigantic and bewitchingly arresting ring-system. The planet itself is another ball of superexcited gasses and storms, but your craft’s sensors are immediately drawn to the biggest satellite, Titan: here is the first glimmer of hope you’ve had! This moon is massive enough to be a planet in any other company (it’s only about 20 percent smaller than your own home world, and what’s more important, its atmosphere has ample traces of complex organic compounds (carbon dioxide, hydrogen cyanide, and precious water), held in place by a specific gravity strong enough to suggest chemical activity at the core. Saturn throws off energy of its own (in excess of the meager amount it receives from the distant sun, that is), and this moon Titan has the rudiments of livability.
But alas, it’s only the rudiments. The atmosphere may be dense, but the place is brutally, unworkably cold, and a part of its orbit takes it outside of Saturn’s protective magnetosphere, exposing it to the lethal bombardment of open space’s radiations. It won’t do, and reluctantly you move on.
What your instruments show you next you cannot believe until you draw near enough to see it: vast Jupiter, larger even than Saturn, a towering stillborn star, more massive and throwing off more energy than all the previous planets combined. Stunned, terrified, you watch storm-systems larger than your home world march with awesome majesty across the gigantic gas giant’s endless cloud-seas. Here is a monster world that can take a straight-on impact from a comet with barely a ripple to the surface of its eternal winds. Hydrogen, helium, ammonia, innumerable traces of other compounds, but it doesn’t matter: this place is just too big, too violent in all its dimensions and properties. You don’t even waste time examining the largest of the huge crowd of moons; they all lie within the monster’s magnetic field, constantly bathed in the lethal radiations trapped in the planet’s field-shadow. If any life can live here, it’s life like none you’ve ever known or would ever want to meet. You’re bitterly saddened, but still relieved to move away from this roaring, pounding cyclone of chaos.
Your sadness turns to desperation as your ship suddenly finds itself in another intense band of asteroids. The system’s star is much closer now, and yet all you’ve encountered is fierce wilderness. Your hopes hang entirely on your knowledge of theoretical planetics: the basic building-blocks of life (oxygen, water, stable carbons) are most likely to occur in a discreet range of temperatures – anything too cold prevents processes from moving, anything too hot breaks the molecular bonds that hold the building-blocks together. You’re entering what you guess is that range for this star, and so you allow yourself one last hope.
And, amazingly, there it is! The planet Mars, a solid world with a thin but tenacious atmosphere composed mostly of carbon dioxide and nitrogen. A compact, inner-heated world with seasons, fluffy white clouds, and a temperature range from bitterly cold to quite comfortable. A world whose axial tilt and paltry magnetic field provide scant protection from the solar winds but whose soil (and vast underground reservoirs of frozen water) is quite capable of sustaining life. Your life.
|A harsh world, yes, but a garden compared to the rest of this solar system. Your ship’s sensors detect three other planets even closer to the sun than this one, but that very proximity likely means they’d be dense little hell-holes of solar radiation and unstable tectonics, whereas your sensors show this planet Mars to be seismically quite docile. In fact, that docility appears uniform: this world’s boisterous youth seems to have ended some four billion years ago. After much suffering, you’ve found the world of your dreams.||
A NASA image of the Schiaperelli region of Mars. The polar cap is visible at the bottom right.
Countless Earthbound humans over the last seven thousand years can empathize with that scenario, for Mars has been their dream-world too. It’s one of the brightest objects in Earth’s night sky, a tiny red light on a wobbly, bizarre course through the heavens. All the ancient astronomers knew it, and every new generation of telescope was trained first not on the moon, that scorned stepsister of Earth, but on Mars, whose allure has been constant.
That allure gained a shape and a three-dimensional reality in 1610, when Galileo turned his primitive telescope upon that bright light in the sky and saw the dim outline of a world bathed by sunlight. Not a star, nor a comet, but a planet more or less like Earth, which was a revolutionary break with received knowledge (the Bible makes no mention of other planets). Fifty years later, Dutch astronomer Christian Huygens studied Mars clearly enough to detect rough scratches on its surface. In 1877 Giovanni Schiaparelli studied the planet for months and drew his famous canali on his map of its surface, and those ‘canals’ gave rise to half a century of frenzied speculation about life on the red planet. In the scientific community of the time, that frenzy reached its peak with Percival Lowell, who turned his telescope on Mars and reported not only an extensive network of canals but the reason for them: Mars was obviously a dying world inhabited by a race desperate to tap ice caps for the planet’s only remaining water supply. Most serious scientists wanted nothing to do with Lowell’s ideas, and scientific journals wouldn’t publish him – but when he wove his tales of noble race on a doomed, distant world, you could have heard a pin drop on the floor of Boston’s Horticultural Hall. It was the perfect interplanetary myth.
|It was, to put it mildly, followed by lots of other myths. The grandest of them all was that of Edgar Rice Burroughs, whose Martian tales (in which its inhabitants called their world Barsoom) were a gaudy space opera of villainous multi-armed monsters and valiant swordsmen-heroes who greeted each other with a hearty ‘Kaor!’ The most sinister of these early myths was written by H. G. Wells, whose Martians in The War of the Worlds came to Earth to consume all human life. Arthur C. Clarke’s The Sands of Mars, Ray Bradbury’s The Martian Chronicles, Robert Heinlein’s Stranger in a Strange Land – these and countless other science fiction tales took the prospect of an inhabited neighbor-planet and embraced it.|
Comic books and cartoons followed suit, with everything from DC Comics’ caped, heroic Martian Manhunter to Looney Tunes’ tutu-wearing (and perhaps connectedly, very, very angry) Marvin the Martian.
Pity poor science, forced to compete with such showboats. Although the contest hasn’t always been entirely one-sided, and the results haven’t always been discouraging (it was Bradbury who pointed out that dreams often motivate such mundane things as space programs); the governments of the United States and the Soviet Union in the 1950s and ‘60s could have expected very little practical payoff from their various probes and launches to examine Mars, and yet those probes and launches happened (to generally disastrous results, as the science of doing it all was gradually learned). The ‘70s saw the Viking probes successfully orbit and land on Mars, and their data confirmed the gradually accumulating picture of a planet quite different from the desert wonderland of fiction. This, it turned out, was a frigid, nearly barren world, a world whose topography bore clear evidence of an active and perhaps aquatic distant past but a world in deep slumber now.
Scientists took this sobering news in stride, mainly because they were quickly being buried in new data about what kind of world Mars was instead of only what it wasn’t. There were massive volcanoes (including Olympus Mons, rising a staggering 13 miles from the plain); there were gigantic fissures (the longest of which, the Valles Marineris canyon system, is four times longer than the Grand Canyon, making it the largest canyon system in the solar system; there was clear evidence suggesting those extensive underground deposits of water ice; in a beautiful, oddly comforting touch of home, there were even wispy, evanescent white clouds drifting across the Martian sky on clear days, their faint shadows racing across the ground below.
The Pathfinder probe followed in 1996, and more recently – and more spectacularly – the mobile landing craft Spirit and Opportunity in 2003; there steadily widened a picture of Mars no less exotic in its own way than the science-fantasy tales of previous decades. Here was a near-miss Earth, a planet of comparable size but far less specific gravity, hence no ability to retain extensive atmosphere, hence no chance of a protective ozone layer, hence no greenhouse effect to trap moisture. Fissures and rock-faces on the planet’s surface strongly suggest Mars had all of these things very early in its history, three of four billion years ago– and then lost almost all of them to interstellar chance. Mars has no oversized companion moon as Earth does; there’s no counter-stabilizing element to its axial pitch and yaw. Likewise its core is likely not molten as Earth’s is, thus no strong planetary magnetic field, as Gregory L. Vogt writes in one of a recent trio of books devoted to the red planet, Landscapes of Mars: A Visual Tour:
Another age-dating clue came from magnetometer studies of Mars. Mars is almost devoid of a dipolar magnetic field. In other words, future Martian explorers would find a compass useless. Earth has a planet-wide magnetic field that is generated by the slow movement of molten iron in its outer core. A lack of an easily detected bipolar field indicates that the core of Mars is largely solid. However, it wasn’t that way in Mars’s early days.
Young Mars, Vogt writes,
… had an active core and an accompanying magnetic field. However, unlike Earth, it did not have the size necessary to sustain internal heat and core movements over 4 ½ billion years. Today, only remnants of its magnetic field remain.
Landscapes of Mars is a thin, oversized picture book; some of its images are in 3-D (the glasses are included) to better simulate the experience of standing on a Martian plateau or at the foot of one of those great volcanoes. 3-D technology has never really worked well enough to justify its popularity, but even so, you can appreciate the you-are-there enthusiasm they’re meant to encourage. Vogt himself is full of that enthusiasm. In his book – as in all three of these books – the goal of the narrative is to someday see a human footprint on the red sands of Mars. Vogt not only believes this should happen, he thoroughly expects it will, and he casts his prose accordingly:
A mission carrying people to Mars will be daunting to plan. Travel to Mars is way above and beyond the challenges faced before the first Apollo flight in 1969. With chemical rockets, the Moon is three days away. Mars is three to six months away, depending on how fast the vehicle can travel. Furthermore , Mars astronauts will have to remain on Mars for twelve months before Mars and Earth are in favorable positions for a return. The quantity of food, water, oxygen, and rocket fuel needed to support a two-year mission is far greater than the carrying capacities of any rocket being planned. Such a Mars mission will require a host of technologies and scientific breakthroughs. Robotic greenhouses and oxygen, water, and rocket fuel processing plants for returning to Earth will have to be sent in advance of a crew. Only when the infrastructure of a Mars base is up and running will people risk the trip. But what an adventure it will be! Perhaps future Mars explorers will discover new forms of life. Then, for the first time, we will know for sure that Earth is not the only oasis of life in the universe.
And central to this destiny of Mars-trekking is that the place is worth visiting in person, a worth it apparently can only achieve in one way – by virtue of somebody, or something having trekked it before mankind. Central to all three of these books, central indeed to virtually every word written about the planet Mars since words were invented, is one concept and one concept only: life on Mars. Without some variation of that, Mars becomes just another barren rock in space, topographically interesting, possibly, but certainly without magic. With some variation of life, Mars becomes an almost unbearably intensified focal point of endless hopes and dreams. Each successive Mars probe has taken a greater and greater hammer to the idea that the planet might currently be home to life. The earliest orbiters ruled out crops, canals, cities, and animal life: no Barsoom (at least not in the last three billion years). All later ones have confirmed this initial impression and worsened it. The best science can hope for now are Martian microbes, the putative fossils of which once briefly made headlines, as Vogt relates:
Scientists did have a brief thrill when in 1996 a team of NASA scientists announced the discovery of what appeared to be fossil bacteria in Martian meteorites. A small class of meteorites, found in the Antarctic ice fields, is believed to have come from Mars. … It is hypothesized that major impacts on Mars would have kicked Martian rock into space and some pieces would randomly find their way to Earth. The proposed Martian meteorites have the identical atomic makeup that orbital spacecraft and landers have identified on Mars. The Martian meteorites are chemically different from lunar rocks (collected by the Apollo missions) and from the usual meteorites found all around the world.
If you detect a certain high-pitched note of defensiveness hovering around that quote, your ears aren’t deceiving you. All three of these books sound the loudest on the possibility that life might somehow still exist on Mars. Much weight is placed on so-called extremophiles, as Kevin Nolan puts it in Mars: A Cosmic Stepping Stone:
It is only in recent decades that entirely different types of ecosystems have been discovered in some of the most extreme environments on Earth, inhabited by types of organisms called extremophiles. For example, extremophile microorganisms have been found within the rocks of the oldest and driest deserts of Antarctica. Other types of extremophiles, called thermophile and hyperthermophile organisms, thrive in total darkness at temperatures well in excess of 100 degrees C and at normally crippling pressures many kilometers down on the ocean floor, feeding from chemical nutrients from hydrothermal vents located at tectonic rifts. Ecosystems have also been found within the most acidic, alkaline, and saline environments known, and one microorganism, Deinococcus radiodurans, can even survive radiation doses typical of nuclear reactors. As varied and extreme as Earth’s environments can be, virtually all can support life. It seems, historically, that we have underestimated both the diversity and the robustness of life and may continue to do so.
And in case you missed his point, he stresses it again, with an eagerness charming enough to lead his vocabulary astray (truth be told, none of these books is exactly Ibsen):
… the discovery of extremophiles in the harshest of Earth environments quenches [sic] the argument that Mars cannot harbor life because conditions there are too harsh. If life emerged there, it is possible that it found ways to survive.
You can find this same point being made in A Passion for Mars: Intrepid Explorers of the Red Planet by veteran NASA reporter Andrew Chaikin. His marvelously-illustrated book is a long love-letter to the hundreds of men and women whose childhoods were – like Chaikin’s – inflamed with science-fantasy visions of Mars. It’s entirely understandable that these people, even more so than the general public, would be unwilling to relinquish the dream of alien life, however minuscule:
Living things have been discovered in all kinds of places long thought too hostile for life – in volcanic rifts on the ocean floor in temperatures above the boiling point of water, in lakes nearly overloaded with salt, and in waters that were extremely acidic or alkaline. Even in the frozen deserts of the Antarctic Dry Valleys, there were organisms living inside rocks, just far enough beneath their surfaces to be sheltered from the harsh environment.
A Passion for Mars is the most winning of these three books, by a considerable margin. Vogt’s picture book is, despite its state-of-the-art glasses, somewhat one-dimensional in its relentless cheerleading (there might not be that much water in Mars, and men may never go there, after all). Nolan’s prose can be both turgid and slightly hectoring:
We wouldn’t dream of sending robots to explore the remote Amazon rainforest or the Antarctic, for example; not just because we can now travel to such remote locations, but also because of the nature of the work – field tests, in situ analyses, and real-time adaptation of strategy and techniques. There is also the human factor: the interaction with things that bewilder, incite, or inspire scientific creativity. All these things would be severely curtailed if the work were only performed remotely.
But Chaikin’s book, though its pages are full of slightly maladjusted social misfits wearing pocket-protractors and exceedingly thick glasses and professing a (no pun intended) universal admiration for goofy American cosmologist Carl Sagan (in my country we would refer to these people as nerden, I’m afraid), is the only one of the three that manages to capture the zeal, the forlorn hoping, the sheer amount of need at the back of mankind’s various lunging attempts to explore this tantalizing world roughly 40 million miles away on a good year. At every juncture, during every tense moment in all the various mission control rooms, Chaikin is there, dramatizing it all and letting his readers share in the heartbreaks and the small triumphs in a way even the best photographs still can’t do. As he narrates the story, we can almost feel it unfolding:
… they received a black-and-white, high-resolution panorama that became the most celebrated picture of the entire mission [the Viking 1 mission]. Taken when the sun was low in the morning sky at Chryse, it revealed a part of the landscape they hadn’t seen before. A whole field of bright drifts filled the frame, their gently sloping surfaces glinting in the sun. Scattered among them were rocks of all sizes, including a huge boulder – it was the size of a desk – no more than thirty feet away. Backlit by the morning sun, the scene was not only superbly detailed, it was undeniably majestic. [Viking Lander imaging specialist Tim] Mutch had a friend who’d been a photographer for Life magazine, and when he saw the image he said, “That a good picture.” Mutch responded, with some pride, about the technical details of the image, but his friend said, “No, you don’t understand – it’s a really good picture.” Viking 1’s cameras had done something that wasn’t in their design specs: They’d revealed the beauty of Mars.
|That beauty isn’t what generations of early dreamers envisioned, but then, true beauty is always unexpected. We have no canal-building inhabitants of a dying world, no rapier-wielding bravos of Barsoom; we have instead a sparse and arid cold clarity, an ochre world of missed chances and tough breaks, an unlucky Earth clinging to the smallest remnants of life, and if there are Martians, they’ll be microbes, hunkered down deep against the ravaging solar winds. There’s a sharp bite of disappointment in this, no denying it: if there is thinking life on some other world, that world won’t be in this solar system – no identical siblings for Earth. But our long millennia of dreaming and our centuries of observation and our decades of exploring have revealed to us a world with bright sunrises, cheery wisps of cloud in the cold, thin sky, and perhaps, every so often and gone before you know it, a quick curtain of rainfall here and there. Voyagers through the various pugilistic annihilations of open space might consider that miracle enough, and maybe so should we.|
Astrid van Sarisgaard is a graduate student in astronomy in Oslo who has been fascinated with interplanetary science for as long as she can remember. This is her first publication in English.