Authors: Rod Pyle
And what an image it was! As previewed in
chapter 1
, the
slow, strip-by-strip buildup of that first view of Mars was a suspenseful, thrilling moment. As the image was assembled on the giant video screen, one vertical strip at a time, it revealed pebbly, rocky soil, with a portion of the lander's footpad to the right.
The next image was a better press moment: a 300-degree black and white panoramic of the horizon. While Chryse Planitia may not have been the most daring landing site, it was still a dense tapestry of rocks, sand, and typically Martian elements, and would give geologists sufficient data to argue over for years. The next day, a color image was sent, and earthlings finally saw Mars for what it is: a fantastically alien environment with hauntingly familiar elements. We know that it is not home, but we can imagine it as such.
The early color images had problems, however; the sky appeared to be an earthly blue and the soil reddish-pink. Later, more highly corrected imagery shows a salmon sky and an orange-ish landscape. There is art as well as science in the discipline of planetary image manipulation, and it took those image-processing experts, pioneers in dealing with color images from space, a while to get it right.
Unfortunately, JPL was under extreme pressure from the press to get the color images out. What should have taken a week of color calibration was done in hours, and the sky hues were off. When the corrected version was later presented with a properly adjusted pink sky, the press corps booed. Some asked, tongue firmly planted in cheek, if the sky might be green tomorrow. It seemed that there was a strong desire to see Mars with a sky much like Earth's; not some alien tone of pink.
The scientists were dumbstruck. It had never occurred to anyone involved how important the images from Mars would be to people at large, nor the intensity of the emotional reaction to them. It was a PR lesson well learned that would pay off in later missions to the Red Planet.
During these early phases of the Viking lander's mission, a
meteorology boom had also been extended, and it began what would be over six years of Martian weather reports. The suite of instrumentation was designed to track the minutest qualities of the Martian day and night.
The values of the Martian atmosphere were confirmed: quite thin, at about 0.09 pounds per square inch (PSI) (compared to Earth's 14 PSI). This thin veil is composed mostly of carbon dioxide.
Lacking the weather-altering influence of oceans, or indeed any standing water, Martian weather turned out to be fairly predictable. The average temperature was -67°F, with a rare high of about +70°F and an equally rare low of -250°F (at the poles). Viking was able to measure much of this variation over a span of years, yielding very consistent results. At the lander's location in Chryse Planitia, the range was a comparatively moderate -22 to -139°F.
The thin Martian air changes temperature quickly when exposed to the sun, and with no oceans to break up the vast deserts, the resultant winds can be fierce. And these often become raging dust storms dwarfing any in the solar system, as witnessed by Mariner 9. Wind speeds measured by the Viking landers averaged about 10 mph and peaked at about 70 mph, though much higher speeds have been hypothesized for other parts of the planet. But with the very slight density of the atmosphere, the effects of even these high winds are much less than an equivalent speed on Earth—about a tenth as much.
Nonetheless, despite the low impact of these winds, it was a challenge when the Viking landers had to sit out a series of three global dust storms over their span of operations. The grit wrought havoc with the mechanical and optical systems. But both landers soldiered on, and the data they returned to Earth advanced our understanding of Mars one thousandfold.
Things with the Viking 1 lander were going swimmingly. Then the first gremlin took hold: the seismometer, designed to detect
“Marsquakes,” was not working. The mechanism that had been intended to protect it during the violent assault of launch was still working, and too well. The detector was stuck in the safe position and was not responding to ground movement. As it turned out, a pyrotechnic device intended to disengage the retaining pin had not fired, and it remained in the launch configuration, which was useless on the ground. They could only hope that the Viking 2 lander did not repeat the trouble. It did not, and while it later provided for only one data point instead of the hoped-for two, the information gleaned from it was invaluable in evaluating the inner structure of the planet.
Then, on the third day, a problem that would be familiar to a later generation of Mars engineers cropped up: the lander began to think for itself—to rebel. The UHF transmitter, its sole link to Earth, was designed to operate in three power settings: one watt, ten watts, and thirty watts. For some inexplicable reason, it arbitrarily switched from thirty watts, its most powerful and effective setting, to a feeble one watt. The lander was getting bratty. The next morning, in keeping with the toddler analogy, it spontaneously switched back to thirty watts. After a few more tantrums, the transmitter stayed in the high-power mode until shortly before the end of the primary mission phase, when ground controllers reset it down to the ten-watt setting to conserve power. The ghost in the machine was silent…but only for a moment.
Soon the sampler arm, which was the only way to feed soil to the life-science experiments, became stuck. This ingenious device extended from just a few feet stowed to about ten feet extended.
3
It had been run out to nearly its full length to grab a sample, and then…it stopped. The worst nightmare of unmanned surface exploration of another world had just arrived. One of those little problems, an occurrence that could be solved by one single, swift kick to the lander, were someone there to do so, had taken hold.
The arm would not budge.
It didn't take long to assess the problem. A locking pin that
was designed to fall out once the arm was deployed had not done so. Working with a twin of the Viking lander not far from the control room in Pasadena, technicians were able to duplicate the problem and come up with a solution. A few days later, all was ready. The command was uplinked; twenty minutes later, it arrived on Mars and was scheduled to be executed. The wait was excruciating. Eventually, images returned from the Viking cameras showed a pin-free sampler arm moving as designed. The mission went forward.
On July 28, eight days after arriving, Viking 1 reached out to grab some red soil. It was much slower than it sounds; these things are done with great caution and delicacy. The dirt was slowly winched back as the arm retracted and swung over the lander to deliver it to the experiments on board. But there was, of course, another problem. One of the experiments, the Gas Chromatograph/Mass Spectrometer, did not send a signal confirming delivery of a sample. On Earth, groans all around. There were a number of reasons it might have indicated failure: there might not have been enough soil to fill all the instruments, or it might be hung up in the feed trough, or the sample indicator might be faulty, or…or…
And there was a larger problem: each of these experiments was a one-shot deal. Once filled, they could not be emptied. So if they fired up the GCMS oven, and it was empty, they would have wasted one of the chambers on nothing but thin Martian air. The final decision was to try again, and dump some more soil into the chamber in question. That would solve the problem either way; it would fill for sure!
Then the sample arm jammed again. Oh, the thing had gotten some soil and begun to retract, but had stopped short of delivering the sample. Furthermore, it appeared to be unable to do any more work at all. This was not good.
After studying the problem on a ground-based twin of the lander, technicians saw that the arm, as it flattened into a metal
ribbon, tended to kink-up under certain conditions. The incredibly ingenious design of the arm was its downfall. While the boom looked like a chrome pipe, it was actually constructed of a spring steel, not unlike a metal tape-measure. So, when retracted, the entire boom was wound onto a drum, flat like a ribbon. As it extended, it sprung back into shape as a tube and became rigid.
They went back to the control room. A new set of commands were issued, carefully designed (a) to give the thing plenty of time to operate, slowly, and (b) to operate only in a specified temperature range (to avoid extreme cold), and (c) to pace the commands in such a way that the motor was given a chance to operate in the most reliable fashion. To everyone's relief, it worked (and later in the mission the temperature restrictions were removed, without drama). Finally, the samples they had so coveted were delivered where they needed to go. It was time for Viking to fulfill its destiny: to determine if life, or at least organic compounds, existed on Mars.
Of course, this operation bumped up once again against the basic assumptions and philosophy of the mission designers. While everyone involved knew that looking in two fixed sites on a planet the size of Mars, grabbing random samples, and expecting to find something alive was a long shot, the press was not so shy. Expectations were high, and the pressure was immense.
With soil delivered, the devices were triggered. Nutrients were squirted, water added, ovens fired, and measurements taken; all with the greatest of care. What would the result be?
The soil samples were baking, the machines measuring. These samples had be selected with the greatest of care, as scientists would analyze images from the lander of surrounding terrain, pick an area, and carefully scoop up some soil. They even had the arm push a rock or two aside to expose “virgin” soil beneath, relatively unaffected by the sun and wind, and took a sample from there. It was painstaking work, and the science team was understandably anxious. Optimism on the part of these people ran the gamut from “I think we will find something” to “I feel it
extremely unlikely…” (note the profound reserve inherent in the statements). But in their hearts, all those involved wanted the same thing: a strong indication of some kind of biological activity.
And then, faster than anyone anticipated, results were in. The signs of life were bubbling up inside the ovens and wetted sample containers. It seemed almost too good to be true!
There were, you will recall, three life-science experiments (the fourth such device, the Gas Chromatograph/Mass Spectrometer, was actually proficient at finding
any
organic materials, living or not). First, the Gas-Exchange experiment would indicate signs of living metabolism if microbes in the sample were flourishing inside its container and the enclosed environs. Second, the Labeled-Release experiment would measure decomposed organic waste if the microbes fed on the nutrient solution added to the sample. Third, the Pyrolitic-Release experiment would detect gases released from any synthesis of organic compounds in the soil.
And just like that, in that order, the dominoes fell. The Gas-Exchange experiment showed a buildup in pressure, a sign of activity within. Then the Labeled-Release experiment demonstrated a radioactive signal, seeming to indicate that something in the soil had metabolized and released the radioactively labeled gas. Finally, the Pyrolitic-Release experiment gave readings as well. The problem was that the readings from the experiments were not quite right. They ascended too quickly, and then decayed in an odd set of timings. Whatever was in the soil was responding all right, but not in the way predicted. It could be life, or…
After much head scratching, soul searching, and in-the-trenches analysis, a less appealing picture emerged. The final straw was that the gas chromatograph had not demonstrated anything organic in the release. It appeared that some kind of raw chemical reaction was taking place and
mimicking
life. All indications were that there was some kind of nasty oxidant in the soil (which was later confirmed to be a high level of perchlorate), which was reacting with elements of the experiments to provide false and
misleading readings. Of course, not being there to look more closely, and to take samples into the lab and work them over with more sophisticated equipment, team members could only guess.
The team split into the “life” and “soil-chemistry” camps, with ill-defined lines between them. Some seemed certain; more straddled the divide. To this day there is a “we found life” camp, surrounded (and outnumbered) by a “we found chemistry in the soil” camp. The debate goes on, and will not be resolved until—possibly—the mission of the Mars Science Laboratory, now planned for a 2012 landing.
Then, one by one, the machines of Project Viking died. Working well beyond their predicted life spans, time and wear caught up with the spacecraft and they surrendered to Mars. First, the Viking 2 orbiter suffered a propellant leak and was deactivated by JPL controllers just twelve days shy of its two-year operational anniversary. Then the Viking 2 lander suffered a power failure and was unable to continue operations, ending its three-year, seven-month career. The Viking 1 orbiter met a more respectable demise: it lasted four years and two months on the job before depleting its maneuvering fuel. Then, unable to reorient itself to continue full operations, it was deactivated by JPL controllers.
But it is the Viking 1 lander's story that touches the heart. This plucky outpost was the last survivor of the quartet, and after almost six and a half years of operations, was at the time the grand elder of all things earthly on Mars. It had even been fondly renamed the Thomas Mutch Memorial Station, after a much-beloved member of the Viking team who had recently died in a mountain-climbing accident. But its long run ended in November 1982. Still sending back weather reports like a lone observer in a distant posting, it was due for a software update. With its plutonium power supply, it should have been good for many more years. But there was an error in the last batch of code sent by JPL; somewhere in the copious binary, there was an errant command that caused its radio dish to rotate down toward the sands below.
Like a loyal servant, it complied, and contact with Earth was lost. Despite diligent efforts from JPL, there was no further contact, and that was that. Nobody knows how long Viking 1 continued to “stare” into the cold desert wastes of Mars, awaiting another command that would never come. There may well be some electrical current flowing in its nuclear heart to this very day….