The Viking exploration of this new world had been going badly. The site of the original landing appeared at first ideal: a low, sandy locale protected from the winds, on the edge of the polar cap but far enough south for daytime temperatures to rise well above the freezing point of water.
The objective: to determine if this new world was habitable and/or inhabited. The Viking team, in addition to this prime observation, also sought to carry out several subsidiary determinations, among them a detailed mapping of the landing site, assay of mineral and chemical resources, and suitability of the site as a permanent settlement for future missions and more extensive exploration.
In the probe for indigenous life-forms, the Viking Project met with almost immediate success. The range of fauna and flora astounded those who had planned the mission, and data relayed back made it apparent that the diversity of ecology equaled, if not surpassed, anything humanity was familiar with at home. The remote exploration proceeded, the equipment exceeding its original design specs as new discoveries continued to be made.
Then trouble began.
The Viking team noticed it as an increasing resistance of certain local organisms to the presence of the craft which had come so far to investigate this semifrozen world.
Day by day this hostility increased, until, with key samplers destroyed and with the ultimate failure of the mission inevitable, the mission directors decided to withdraw. The Viking Project, pending possible future reassessment of the dangers, was terminated, the brief interest in this world dying like the scattered scraps of advanced technology left so far from home amid the drifting sands and polar winds—left to the rightful inhabitants of North America for almost another half millennium!
Thus ended the first Viking expedition. The Norsemen (my ancestors!), repeatedly assaulted and decimated by Indians, returned to Greenland, abandoning their brief experiment on the new continent. Little could they dream that, centuries later, others—better equipped both politically and technologically—would succeed where they had failed. Their retreat, partially because more immediate riches were available through raiding the already developed European continent, abandoned perhaps the richest developmental prize in the history of the human race. It is ironic, therefore, that from the unique environmental wealth of North America should follow a second Viking experiment.
It is by virtue of the untapped abundance, area, and isolation of North America that such an entity as the United States could grow, relatively undisturbed, to become the technical and social leader of the planet. It is no accident that it is this nation, dominating North America, which has sent explorers to another world, or that it is about to send electronic surrogates under the code name Viking to Mars. And therein lies the deepest irony.
This new Viking Project, unlike its predecessor, will fail not through discovery of life indigenous to its destination, but through the lack of such evidence. If Viking does not detect life in some form or, at least, strong evidence of organic molecular structures on Mars, then public interest in continued exploration not only of Mars but of all space will plummet. Who will want to waste badly needed money exploring a dead Solar System?
And thus, like its historic precedent, another Viking Project will have occasioned the abandonment of a new world. The result of this tendency toward historical repetition, however, may not follow the script beyond this traumatic withdrawal. There are those who feel that exploration and development of the Solar System may be, in its ultimate form, a kind of social "safety valve." That, without access to the immense new resources and technologies of space, life on Earth at this critical juncture can only turn in one direction—downwardas nations and people fight to monopolize dwindling resources amid rising populations. At best, repres sive measures limiting population growth, consumption, and surplus activities will not leave sufficient resources for a second look at Mars, perhaps when future interest quickens. At worst, the abandonment of the resources of the Solar System can mean increasing conflict between the have and have-not nations of Earth, conflict ending in nuclear war and the destruction of all life on Earth.
In this light, with not only future exploration of Mars and the Solar System hanging in the balance, but the very continuance of life on our planet perhaps dependent upon the results of Viking's discoveries on Mars, why is the vital mission doomed to failure? And, while we're asking interesting questions: How did we ever get ourselves into this particular box? And a final one: Is there a way out?
Let us begin with question number two.
We have been brainwashed. The year following the planned Viking landing on Mars (1977) will mark the Hundredth Anniversary of the "birth" of the canals. It was during a particularly close opposition, late in the summer of 1877, that Giovanni Schiaparelli, from the Observatory in Milan, noticed markings on the large disc of Mars which he called canali, meaning "channels." Through faulty translation and a predisposition to ,belief in an inhabited Mars, even then, his canali became "canals."
And everyone knows you don't get canals without canal-diggers ergo: Mars must be peopled by somebody with a penchant for excavating a great quantity of Martian dirt.
But it was an American (who else?) with a natural talent for Madison Avenue tactics, Percival Lowell, who really sold Americans (and anyone else who'd listen) on the idea that there were Martians busily operating power machinery all over the Martian surface, frantically canaling water (a very scarce commodity on Mars) from the polar caps to wherever it was needed more. Lowell, who erected an observatory in Arizona solely to study the planet, built up an elaborate romantic picture of struggling Martians coping with the inexorable desiccation of their dying planet, uniting in the face of planetwide disaster and pooling social and technical talent toward one objective—survival.
Throughout this last century there have been diverse and fascinating indications of how deep in our society the idea of Mars as an abode of life has been ingrained. At various times prizes have been offered for detection of life outside Earth—with Mars excluded as being too easy a target. Serious communications have been proposed with Martians, some involving such gargantuan schemes as bulldozing a huge right triangle in the Sahara Desert to illustrate the Pythagorean Theorem. It was to have been filled with oil and lighted at night, thus conveying to the Martians that not only could we move a lot of sand, but we understood geometry and had discovered fire!
Most fascinating was the order given by both the Chief of Naval Operations and the Director of the US Army Signal Corps to maintain radio silence during the Mars opposition of 1924, in order that radio communication from the Martians could be clearly heard. The Army even had its chief cryptographer, William Friedman, standing by, just in case. As history now shows, Mr. Friedman did not achieve immortality through deciphering a message from Mars, but did achieve notoriety later, during World War Two, by cracking the Japanese code.
Oddly enough, during this period, with Lowell drawing vociferous- attention to Mars (and indirectly to the other planets which had been largely ignored by astronomers), said astronomers were piecing together a Martian environment decidedly unhealthy to such living organisms as they were familiar with. This increasing disparity between the romance of Mars and the reality of Mars seems to have gone largely unnoticed by the public. The blame for this schizophrenic attitude can probably be laid to the rise of a new literary art form: science fiction.
It has long been lamented by some people (mainly SF writers) that the "literature" is largely ignored by the general public. I believe this is inaccurate. Backed by a cover of scientific plausibility, one after another of a whole series of convincing writers—Weinbaum, Heinlein, Clarke, Bradbury—an endless list, successfully modified the Martians each time the astronomical community modified Mars. And they made everyone believe them.
We believe in Martians, partially, I suspect, because we want to believe in Martians. Subconsciously, we have always been lonely; ergo, our ready acceptance of any evidence that there is life elsewhere in this Universe. And Mars is so handy . . .
The beginning of the end of this cozy picture of next-door neighbors started in 1965. That was the summer Mariner IV made its historic flight past the dusky planet and televised back twenty-two images of a Mars for which nobody was prepared. Gone were the canals and the great Martian civilization. In their places were craters, craters, and more craters. And the Word went forth from JPL: . . . "Mars is dead, cratered and battered like the Moon, and thus it has been for the life of the Solar System. Long live the Martians who aren't, and never were . . ."
It was a shock. Gone forever was the land of "The Martian Chronicles," replaced by the sterile hostility of a bleak (to John Q. Public) lunar landscape. I firmly believe the decline of interest in space began on the afternoon the evening editions carried front-page photographs and stories destroying, at last, the Martian legend.
We now fast-forward the film to 1969—the summer of the Apollo miracle.
I can remember being at JPL, with CBS, while Mariners VI and VII beamed back hundreds of photographs and data as they flew by Mars the month following Apollo 11. Called to comment on the air about the heretofore unseen Martian features, all I could point out was the dissimilarity of one Martian crater to another and their group dissimilarity to lunar counterparts. There wasn't even left the possibility of Martian life growing in the craters, as the radiometers carried by the spacecraft eliminated at a glance the hope of water on the planet. Those brilliant polar caps which everyone had always pointed to as evidence for similarity between Earth and Mars turned out to be solid carbon dioxide—dry ice! And, of course, there was no oxygen detected, nor nitrogen. I can still remember the flap about one of the experimenters who thought he'd detected ammonia near the south polar cap (indicative of some biological process). In the light of all the negative evidence, particularly the pictures, we had an enormous amount of trouble getting even that ray of hope on the Cronkite News. And, as it turned out, he'd discovered, not ammonia, but a heretofore undetected absorption band of solid CO2! Small comfort that, if it were not for the enormous extent of the Martian carbon dioxide fields, that particular band would probably have gone unnoticed.
Thus, in the late summer of '69, the final nail in the coffin of Martian life was hammered home to the TV audiences. Coming after the climax of the Apollo Adventure (which had been billed, for years, as an ending, not a beginning), this cinching of the Mariner IV picture of Mars as a dead, lifeless planet, I feel, firmly turned the national mood toward: "Why bother? Particularly when we need the money so much more at home to clean up the mess technology has made of this planet." It is only, therefore, by the grace of Federal bureaucracy, lead-times, and human inertia (Congress hates to turn off money to projects when more than half of it has been spent), that plans to orbit Mars in 1971 were well underway. If not, we would never have seen the real Mars, through Mariner IX.
Mariner IX, man's first artifact to orbit another planet, succeeded in wiping out the myth of a "dead Mars" by virtue of its ability to stay with the job. Imagine the state of Mars exploration now, if Mariner IX had been a fly-by during that dust storm. The-screams about wasted money would still be heard echoing through the corridors of the Capitol. But, by being an orbiter, Mariner IX was able (repeatedly) to mosaic the entire surface of the Red Planet, from pole to pole, and thus discovered the volcanoes (evidence of an active, differentiated planet); the canyons (beginnings of continental drift, anyone?); the fascinating "laminated terrain" of both polar caps (vast glacial deposits of water-ice and frozen CO2); and the presence of vast Martian "Mississippis" (definite evidence of a much more hospitable Mars, when rain, flooding, and huge river systems occurred throughout the Martian "tropics"). In short, Mariner IX completely upset every conclusion we had formed as a result of Mariners IV, VI, and VII.
Mars is alive (geologically) and holds the promise of life amid a variety of impressive surface topography far more interesting, potentially. than the flat, canal-crossed planet of Lowell.
As luck would have it, with much of the world press (including our three TV networks) gathered at JPL during Mariner IX's approach to Mars, the Great Dust Storm obscured the approach photography which would have immediately dispelled the myth of Mars as a dead planet. Imagine the excitement which clear, pole-to-pole photographs would have created, even before we achieved orbit. Instead, with hundreds of close-ups of the storm (as one wag put it: "Sharp TV of bed-sheets followed by enhanced [by computer] bed-sheets"), press interest quickly evaporated, as did the television cameras. By the time the dust had settled on Mars and the incredible photographs revealing its true nature were received back in Pasadena, about the only reporter left in Von Karman Auditorium was the guy from Aviation Week.
High-resolution Mariner IX TV picture of a twelve-mile-diameter crater and extensive flow ridges indicative of liquid
water at some time in the recent history of Mars. Lack of significant erosion of smallest features (several hundred feet high)
would indicate that Mars, to Cro-Magnon man 12,000 years ago, may have been blue-green, with clouds. (NASA)
But now, three years after Mariner IX, the truth about Mars is filtering out through a sort of "Martian underground." Once again, people talk about Mars with a peculiar light in their eyes. This past summer, the UFO flap was again brought to life by the suspicion that "they" might be returning the courtesy of Mariner IX by coming here. People believe, again ...
Thus we stand on the eve of Viking, our first mission to another planet sent expressly for the purpose of detecting indigenous life. The Mars that Viking will explore is an absolutely fascinating place, indicating in every way that its evolutionary history created conditions in the past far more favorable for life as we know it. Even in its present state, a glaciated waiting world with a thin four-millibar atmosphere (1,000 millibars equal one Earth atmosphere) of CO2, and with less than 30 precipitable microns of free water, certain terrestrial organisms could survive quite nicely on Mars—and have, in duplicated Martian environments, in many labs.
I believe there is life on Mars. I support this belief with a variety of slowly accumulating evidence, from interstellar radio detection of increasingly more complex organic molecules to the detection of some of those in comets; to the enormous range, adaptability and tenacity of relatively pampered terrestrial species, once evolution has begun. At the Laboratory for Planetary Studies at Cornell University, Dr. Sagan. and colleagues have experimented with a variety of techniques to synthesize the "building blocks" of life from simple gaseous mixtures of water vapor, ammonia, methane, et cetera. In all their experiments, by whatever means they use to energize the mixture—electric discharge, ultraviolet light, heat, radioactive decay, even to kicking the flask (even though the good doctor alluded to this experimental technique on national television, I rather doubt its practical applicability in the Cornell experiments!), amino acids, the foundation of proteins, inevitably form, given enough time. And the time, even at Cornell, is usually only a matter of days or, perhaps, weeks. Thus, to imagine an entire planet such as Mars, with a 4.5-billionyear history, not duplicating at least what Cornell and Dr. Sagan have been able so routinely to achieve is very hard to accept, given the presence of essentials. From these simple experiments to a self-replicating structure such as DNA is, of course, another matter; mainly, much more time. But time is one commodity Mars has had as much of as Earth. It is, therefore, precisely to see if this phenomenon called "life" has occurred twice within the 4.5-billion-year history of the same star system, on two worlds with more similarities than differences, that Viking will be sent to Mars.
Why, then, if I believe life is there, do I also believe Viking will fail to find it? Let us follow the Viking Mission profile to the surface of Mars, and find out.
The initial Viking landing will be made, probably, on July 4, 1976 somewhere in an ellipse 80 miles wide by 373 miles long, centered at 34 degrees west longitude, 19.5 degrees north latitude. This is an area known to classical astronomers as Chryse. Mariner IX photography indicates, together with other data, that it is a level sandy alluvial plain, protected from the winds, at the mouth of a series of intriguing Martian features that look like rivers cut by running water.
The exact procedure goes something like this:
Two spacecraft lift from the sands of eastern Florida bound for the sands of Mars on a special version of a Titan/Centaur launch vehicle. Each weighs about 7,500 lbs., a combination Lander/Orbiter. Ten months after launch from Earth, each spacecraft "team" will enter Martian orbit, the first about June, 1976, the second a month later.
The Orbiter, with Lander still attached, goes through a series of scientific measurements of the proposed landing site, including high resolution television. Bad weather, for instance, could force the choice of an alternate site if it doesn't clear within the period the Orbiter can retain the Lander in orbit, about 50 days.
After the decision to land, separation of Lander and Orbiter occurs, behind Mars, with entry of the Lander into the Martian atmosphere at about 15,500 ft/sec. The Orbiter, meanwhile, remains in its very elliptical orbit with the apoapsis (high point) above the intended landing site on the Earth side of Mars; when, at that point in its orbit, it will act as a real-time relay to Earth of data from the Lander.
The Lander, after entry, discards its aeroshell (a sort of heat-shield) and begins its descent by parachute, all triggered by a radar altimeter. During entry, and while on the 53 ft. 'chute, an upper atmospheric analysis is performed. At 3,900 ft. the 'chute is cut loose and three radar-controlled 18-nozzle liquid fuel engines control the terminal descent phase, between 25 and 40 seconds in length. Touchdown will occur at a vertical velocity between 5 and 11 ft/sec., and a horizontal drift of less than 4 ft/sec. And thus the first Viking will stand on Mars, a three-legged 1,200-1b. robot on another world.
Section of 2500-mile-long Martian Equatorial Rift. Feature indicates vast internal forces reshaping surface, belying previous concept of Mars as a "dead" world. Note intricate, tributary-like erosion at heads of blind canyons. Features appear now to be caused by water—flowing in very large quantities. (NASA)
The focus of the entire unmanned planetary program for the United States is Viking. And its prime objective, in accordance with recommendations made in 1965 by the Space Science Board of the National Academy of Sciences, is the search for life. This is also the highest subconscious wish of the American people supporting the entire program. So, there Viking stands, a remote emissary from the green hills of Earth (to coin a phrase) on the reddish sands of Mars. What does it do?
The first thing it does is take some pictures. If we are very lucky, says Carl Sagan, we may see a silicon-based giraffe walk by, and with a camera—snap!—we've got 'im. Therefore, the camera—actually two cameras—system is classified as a biological experiment of great possible value (also, a geological experiment and, when it photographs cloud formations, a great meteorological experiment, et cetera). TV cameras are great experiments, in general. This one, incidentally, is not what you'd normally think of when you say "TV camera." These cameras, located a few feet apart for stereo, are actually nodding mirrors located behind rotating slits above a series of photo-diodes. Each picture will be built up by rotating the slit and nodding the mirror in synchronization as the resulting analog signal is formatted into digital information and fed to Earth in real-time via the Orbiter, or stored for slow transmission_ directly, via the Lander's own S-band dish antenna.
The initial objective will be to build up a panorama of the Martian landscape—low resolution, at first, and later, high resolution, in natural color. Now a problem arises. One of the hopes is that, besides Carl's giraffe, investigators, in addition to sand, sand, and more sand as well as hills, arroyos, and a few rocks, will see a plant. Wouldn't that be fantastic? Land on Mars, turn on the camera, and—zowie!—a genuine Martian cactus. Right? Think a minute.
What would it look like?
Terrestrial plants evolving on the same planet look enormously different. What, then, would an indigenous Martian example of local flora look like, after several billion years of completely independent evolution? But, you'll protest, it has to have leaves of some sort to absorb sunlight. Does it? It may use lenses, or mirrors, or just be a large black blob absorbing all wavelengths and using whatever's left over from photosynthesis, for just plain heat. No, the first problem will definitely be: Is that thing over there a rock or a Martianus indigenous?
Leaving our television experimenters to puzzle over their ambiguous "thing," we shall move on to other experiments this complex robot has brought to Mars. Viking is many things to many people. It carries a seismometer, to detect and locate (if they're big enough) Mars-quakes. One good one of sufficient power could allow us to map the entire interior of Mars, chart its mantle, crust, and core, if it has such features. It would also, presumably, detect the footfalls of Martian elephants if any tried to sneak past the Lander in the dark. Since there is a high degree of skepticism over such organisms (higher, even, than the previously mentioned giraffe), the seismometer definitely is in the geological, not biological, category.
Viking carries an X-ray fluorometer, a very small device (weight less than 2 lbs.) which will zap a sample of Martian soil with X-rays of a known spectrum and detect the resultant emission. The objective: to assay nonbiological elemental constituents of the Martian surface.
This experiment may tell us what trace elements Martians contain, but it will not directly tell us about life on Mars.
Viking carries a set of rather simple but effective meteorology sensors, on a deployable boom which will measure such obvious things as air pressure, wind speed and direction, and relative humidity. Since most of the so-called seasonal activity appears now to be meteorologically related to wind-deposited dust, this experiment should give us good first-hand data on actual Martian weather (oh, yes, temperature will also be noted) for input to a computer forecast of weather generated from planet-wide atmospheric observations carried on by the Orbiters.
This experiment, only very indirectly, is related to the central question of detectability of living organisms on Mars. But more of this aspect later.
Viking carries three prime experiments related to the question: Is there life on Mars? Two of these, the TV system and a device called a Gas Chromatograph Mass Spectrometer, will indicate biological activity through indirect means (unless we see Carl's creature). The TV could detect burrowing (Martian moles?), past sedimentation of a biological origin on cliff walls, or (!) a technological artifact. The GCMS is designed to sniff the lower Martian atmosphere and to detect very low concentrations (less than one-tenth part per million) of such organic compounds as ammonia, methane, hydrocyanic acid, and acetylene—possible indicators of biological activity. In addition, it will detect such "ordinary" atmospheric constituents as oxygen, nitrogen. et cetera. In fact, any species from atomic mass 12 to 200.
This close-up Mariner IX composite reveals extensive evidence of blown and drifting sand. Dunes are approximately
one mile apart, indicating ample sand for several thousand feet vertically as well. Such features appear common to
the present Martian surface. protected interior of crater creates conditions for standing wave pattern. ( NA SA )
In addition to measuring atmospheric concentrations of possible significant compounds, the GCMS has the capability of performing three separate soil analyses of 100-milligram samples. Its limit of three is set by the necessity for carrying a finite supply of hydrogen to flush the released gases through the detectors. When the hydrogen is gone, the soil analysis part of the GCMS will be over. However, the atmospheric analysis will continue until the end of the mission (nominally 90 days after touchdown, although most project people fully expect Viking to operate for at least a year).
The results of this experiment could cause a lot of confusion. Positive detection of organic materials in the atmosphere, particularly if they're seasonally dependent, would indicate possible biological activity, depending on the nature of the molecules detected. Organic materials in the soil, however, could or could not indicate living organisms on Mats. JPL recently produced amino acids under Martian-like conditions by irradiating a mixture of CO2, water, and silicate dust mixed with limonite (a hydrated iron oxide). Thus, even complex organics could be produced abiotically.
That leaves us, then, with the prime biological experiment on Viking, designed to detect living, breathing Martian micro-organisms. The biology experiment is actually three experiments in one, each designed to check the validity of the other, as well as to test separate mechanisms for growth and metabolism of Martian life-forms.
Experiment number one I will call the "Mars-as-it-is-now" experiment. It consists of placing a small sample of Martian soil in a sealed chamber illuminated by an artificial light source which duplicates the spectral and intensity aspect of Martian sunlight. Carbon dioxide, the overwhelming natural constituent of the Martian atmosphere, will be admitted from an onboard spacecraft reservoir "doped" with a percentage of radioactive Carbon-14. After a suitable period, the CO2 will be removed from the chamber and heaters turned on to raise the temperature of the sample to about 600° C. This will drive out all volatiles from the soil, including any CO2 respired by Martian micro-organisms in the sample through photosynthesis. The Carbon-14 tagged CO2, measured by a Geiger detector, will indicate the extent of such photosynthesis.
This experiment, based, obviously, on the assumption (as are all the Viking biological experiments) that Martian life will be carbon-based, will tell us, if positive, that the micro-organisms like the present Martian conditions and will give us an indication of how rapidly the metabolic processes of such organisms proceed. If the experiment detects nothing, then we will begin a long list of, "Well, maybe we landed in the wrong place . . ." or "Maybe the season's wrong ..."
Let's go on to experiment number two.
In this chamber the soil sample is "fed" a special nutrient containing a Carbon-14 tracer. The idea here is that if the organisms digest the nutrient, then, in the absence of sunlight, CO2 will be released as a waste product. Again, the radioactivity associated with the released, tagged CO2 will indicate metabolic activity.
Experiment number three is essentially the same as number two, with the exception that not just tagged CO2 will be measured but, by means of a gas chromatograph, the complete evolution of respired gases in the chamber will be monitored as a function of time. These will include such exciting compounds as hydrogen sulphide, hydrogen, hydrogen cyanide, nitrogen, oxides of nitrogen, ammonia, oxygen, and methane. The obvious advantage here is that it is just possible the metabolism of Martian micro-organisms may lead to the formation of gases other than carbon dioxide or' carbon monoxide. This experiment will detect them.
That's it. These three basically very simple experiments are what the future of the American Space Program depend upon. Now, why do I think the sum of all their sampling and heating, detecting and "doping" will turn up zero evidence of Martian life? The problem is Mars.
When I was developing my addiction for astronomy, hanging out among dusty library shelves where sunlight hadn't penetrated in many decades, I once came upon some old Bonestell representations of what the end of the world would look like. I was fascinated by the sight of ice-laden skyscrapers and the sun, framed by the icy tendrils of a frozen bridge, glinting coldly off the surface of a world numbed beneath the cold of a dying star. I can still remember the wonder of contemplating the process whereby the actual atmosphere would freeze and fall to the ground. And there was a sort of wistful afterthought: pity it won't happen here for another five billion years! . . . My disappointment was premature—by about five billion years!
The Mars of Now. Mariner IX photograph covering the planet from North Pole, layered with mile-deep layers of frozen CO2 and H20, to south of the Martian equator. The four huge volcanic piles, Nix Olympica to the left and the other three along a diagonal line to the right, are also visible. The west end of the enormous equatorial rift is just visible at the southern limb. (NASA)
Mars, apparently, is such a planet. Through a combination of its location on the outer edge of the "habitability zone" of the Sun (where water will remain liquid) and the pronounced eccentricity of the orbit (e = 0.093), the Martian climate fluctuates enormously.
Mars is presently in its "frozen atmosphere" glaciated state. Mariner IX photography of both polar caps revealed vast areas of laminated terrain, layered in receding steps, each step containing between 20 and 40 layers, with between 200 and 400 layers in all, each approximately 30 meters high. This amounts to approximately a mile of sediments at each pole, covering several million square miles, and containing, if vaporized, enough frozen CO2 and water to produce a Martian atmosphere equal in pressure to the Earth's!
It is in the polar glaciers, then, that the Martian atmosphere is currently "hanging out." Somehow, in the past, that vast mass of carbon dioxide and water got frozen out, the entire atmosphere "falling to the ground" as in the Bonestell painting, and there it is today...That the process is a continuous one can be seen from the layering of light and dark material making up the "piled-up poker chip" pattern. The light stuff is thought to be the water-ice and CO2; the dark stuff sand and dirt blown there by the periodic Martian dust storms. The length of time it has taken to accumulate these glaciers is presently unknown, but there are some intriguing suspicions.
This fascinating state of affairs seems to be occasioned by the combination of the tilt of the Martian axis, the eccentricity of its orbit (unlike the Earth this has a much greater effect on Martian seasonal temperatures), and the 50,000-year precessional period of Mars itself. Apparently, there are times when these three factors conspire to create a "cold-trap" at the poles.
Imagine a sunny day on Mars about 10,000 years ago. The atmosphere, mostly CO2, a moderate percentage of water vapor and a goodly percentage of oxygen and nitrogen, is pleasantly dense and produces a variety of Earthlike phenomena—rain, weather fronts, lightning, et cetera. Because the pressure is so high, water is liquid on the surface, forming moderately large lakes. Days and nights are not enormously different in temperature, even though Mars is almost half again as far from the Sun as Earth, because of the "greenhouse effect" of the CO2 and water vapor. Martian life (!) through photosynthesis converts the carbon dioxide and water to free oxygen and more organisms. Life is pleasant, as water fills the rivers and lakes around the equatorial region and rain washes the air fresh each Martian dawn.
But Mars is moving inexorably in its orbit and about its axis. Precession tilts the hemispheres farther and farther away from alignment with the orbit at perihelion; and bit by bit as the years slide by, each Martian winter in one hemisphere is colder than the last, trapping a bit more snow and ice, and each summer in the other hemisphere is not quite as warm as in the years before and the snow and ice at its pole melts less and less.
The Martian organisms sense it is Time, once again. The long winter is at hand. Slowly, as the rivers run dry and the water migrates toward imprisonment amid the polar ice-fields, the process of photosynthesis runs down. Organisms prepare for winter and the long period of hibernation until the next Martian spring-12,000 years away. Oxygen, no longer produced in equilibrium with oxidation of the Martian surface, rapidly becomes a trace constituent, along with water. Ozone, the protective ultraviolet screen formed by moderate amounts of oxygen high in the stratosphere, loses its ability to shield the surface from direct ultraviolet radiation. Nitrogen, formerly present in the atmosphere, is now ionized and combines rapidly with surface materials to form nitrates.
The atmosphere, now almost entirely CO2 and without the heat trapping capacity of water, blows with increasing strength between the warmth of the sunlit side of Mars and the cold of the Martian night and poles. Without water to consolidate the surface, increasing quantities of dust are blown high in the atmosphere. The great Martian Dust Storms begin, blanketing craters, canyons, river valleys, and hibernating Martian organisms beneath a deepening layer of eroded Martian sand.
For life, this is ideal, as without significant amounts of ozone to protect the surface from direct UV, any living thing not covered by a thick layer of sand and dust will be irradiated back into relatively simple molecules.
The Martian precession continues, and the polar temperatures become more asymmetrical. At some point, probably during a particularly intense, planetwide dust event, the lower atmospheric temperature over the winter pole drops below the condensation point of CO2 and the Mars we know is born. Within a relatively short period of time, as CO2 snowstorms remove the remaining atmosphere and deposit it upon the polar caps, the loss of the greenhouse effect rapidly diminishes the general temperature, making it easier each winter for more CO2 to freeze and become a layer at the poles. At last the atmospheric pressure stabilizes at 1/1000th of its former value and deposited dust melts just enough each Martian summer to replenish that which is frozen in the fall. The long winter has arrived.
This state of affairs—the Mars we know--probably continues for almost one-fourth the precessional cycle, almost 13,000 years. It is only when both poles begin to receive equal amounts of heat during the year, that this "cold trap" effect can be reversed. Thus Mars exists as an almost atmosphereless, desiccated planet bathed in raw ultraviolet radiation, smothered in fierce, erosive planetwide dust storms and whipped by thin cold winds exceeding, at times, 200 miles an hour, for most of its existence. And yet, evidence exists that, briefly—a few thousand years out of each 25,000—a vast improvement in this forbidding Martian environment takes place.
It is for those brief millennia of spring (when rain-washed zephyrs fill the Martian skies with lightning and the waters again come flashing down the canyons and ancient river bottoms, sluicing through the dust and awakening the sleeping Martians. in their beds) that I believe Life waits.
Thus, with its extended claw, Viking will have come amid the barren dunes of winter to sample mere inches of the surface, the irradiated, sterile wind-blown sands covering the alluvial plain of the ancient torrents of Chryse.
And, all the while, a mere hundred feet or so beneath its ineffective sampler, but as remote as if Viking were still standing on the surface of Earth, the Martians slumber on—awaiting patiently the spring and the rains which will, inevitably, wash away the dust of 12,000 lonely years.
If Viking's failure, through Martian life's sophistication rather than simplicity, results in public disappointment and withdrawal from space, as I foresee, then this could be the consequence:
The Martian spring arrives and with it the pulse of life awakens once again. In the midst of this activity an artifact stands silently upon the plain, rising water swirling about its half-hidden alien shape. It is an ancient emissary from, another world and time. In the cosmic scale of such events it came a breath too early to fulfill its mission and because of that its successors never came at all. They, like their creators, perished shortly after the rejection of the Solar System by the inhabitants of planet Earth, millennia before this newborn Martian spring.
Thus -life on Mars awakes-alone—and thus it will remain.
ABOUT THE AUTHOR
Before becoming a full-time writer, Richard C. Hoagland was Coordinator of Public Affairs and Special Events at the Hayden Planetarium in New York City. Prior to that, he worked closely with Walter Cronkite as Science Adviser to CBS during the Apollo Program.