by Rod Pyle
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….
Despite this unfortunate end, the science and discoveries of the Viking program would benefit future missions and fuel the next giant leap in Mars exploration: wheels.
The year was 1936. The first episode of The Green Hornet was heard on WXYZ radio in Detroit. The first radioactive element was produced synthetically. Adolf Hitler announced the first Volkswagen Beetle®. And Norman Horowitz arrived at Caltech in Pasadena, California. It was the beginning of an auspicious career at both Caltech and the Jet Propulsion Laboratory. He was a biologist by training, but his eyes was trained on the stars…and in particular, the planet Mars.
“By 1959, it was definite that the Jet Propulsion Laboratory was going to be a planetary science lab, and people began coming down [to Caltech] from JPL to see if there was any interest here in planetary exploration.
“I thought [life on another planet] was a plausible idea. Everything that was known about Mars at that time later turned out to be wrong, but [at the time] suggested that there was a good possibility of life on Mars. I had a choice of going into something…taking this golden opportunity to get involved in a new program. And that's what I did. It turned out to be very exciting. Of course, we didn't find life on Mars, but I'm glad I did it.”1
Horowitz made a decision then and there that would affect not just his life, but the entire search for life on Mars. His move to JPL placed him in the Center for Planetary Exploration, where he would become one of the lead members of the Viking life-sciences team.
“The exploration of Mars became the key idea for a planetary program, for obvious reasons, and JPL set up a bio-sciences section to plan for the biological exploration of Mars, with an eventual lander. They asked me to come up and be chief of their section, which I did in 1965. There was a lot of work going on up there in trying to design instruments to fly to Mars for a biological search, and I got involved in that planning. Two of the instruments that eventually flew on Viking came out of that group. The Gas Chromatograph/Mass Spectrometer, which was probably the most important single instrument on the lander, was designed at JPL.
“When I went up there, that was already in process—it had been anticipated that this would be a useful instrument to have on Mars. What I did get involved with in connection with that instrument was making sure that there was a lot of ground-based experience with it. The instrument is based on empirical patterns of breakdown of organic compounds. You take an organic compound and you heat it until it pyrolizes—it breaks into smaller fragments due to the heating. These fragments can be identified by a combination of analytical steps called gas chromatography and then mass spectrometry. The only thing you have to identify the original compound you started with is the pattern of its breakdown products, and you try to infer the nature of the original compound from these breakdown products. There's not much general principle or general theory you can go on; you just have to have a library of results you can compare your actual results with. We did a lot of that during the years that I was there.”
And this was the key to the search for life on Mars—trying to find a way to identify the building blocks of life by remote observation. To do this, Horowitz's team would have to build up a large database of similar reactions working here on Earth. It was not a trip to Mars, for which many of them would have gladly gambled their lives, but was the next best thing to going there.
“Another thing I did was to get the idea for the second biological instrument that JPL had on the Viking lander. NASA called it the pyrolitic release experiment; we used to call it the carbon assimilation experiment. It was an experiment that I developed with two collaborators, George Hobby and Jerry Hubbard. The point of this experiment was to carry out a biological test on Mars under actual Martian conditions. It's hard to convey in a few words the total commitment people had in those days to an Earth-like Mars. This was an inheritance from Percival Lowell. It's amazing: in pre-Sputnik 1 days, in fact, up till 1963, well into the space age, people were still confirming results that Lowell had obtained, totally erroneous results. It's simply bizarre!”
And that was the challenge. Horowitz knew by the time he moved to JPL that Mars was not Earth-like in ways that counted toward supporting life, but sometimes he felt that he had trouble getting others to understand it. Oh, they might pay lip service to the thin atmosphere, the extreme temperatures, and the voluminous solar radiation, but living deep in their hearts was a very different image of the Red Planet.
“A lot of people thought Venus was covered by an ocean. But that was speculative; in the case of Mars, they were making measurements and coming up with the wrong answers. Measurements were made on the 200-inch telescope by…a well-known astronomer—and they were completely wrong. This is just one example. And this was all based on the desire of people to believe that Mars was an Earth-like planet. It wasn't until 1963 that this began to unravel; the first step in the de-Lowellization of Mars occurred in 1963.
“[That] was one infrared photograph taken at Mount Wilson. It was an unusually excellent photograph, showing the infrared spectrum of Mars. It must have been a very dry night above Mount Wilson, a very calm night. They got this marvelous single plate, and it was interpreted by Lew Kaplan, who was at JPL, and Guido Munch, who was a professor of astronomy here…and Hyron Spinrad, a young postdoc working on Mount Wilson at the time. They showed, first of all, the total atmospheric pressure on Mars….”
But even the coldest scientific data must meet with an emotionally charged challenge when pre
sented to the broader community, and history had something to say about the subject: “Back around 1900 Lowell had estimated [Mars's atmospheric pressure to be] 85 millibars…so when the space program started, it was generally accepted that the surface pressure on Mars was 85 millibars, and that carbon dioxide was a small fraction of this; the rest of it was assumed to be mostly nitrogen, as on the Earth.
“So at least [life] was plausible. The Martian environment appeared to be Earth-like, but a very cold and dry Earth-like environment, an extreme form…with all the same elements, with water available and enough pressure so that liquid water could exist at least transiently on the surface. This was a difficult point, to get enough liquid water to support life. With 85 millibars, there was a possibility that you could have liquified water, at least for part of the day.”
But the soon-to-be-infamous Mount Wilson data showed something very different.
“[Kaplan, Munch, and Spinrad's] findings showed that the surface pressure could not be 85 millibars. It looked more like 25 millibars to them. They also identified water vapor in the spectrum; that had never been seen before. They found very little water. And it was obvious that carbon dioxide was a big portion of the atmosphere and not a minor portion.
“Well, this turned out just to be the first step. The next big step came in 1965, when Mariner 4 flew by Mars and found that the surface pressure was more like 6 millibars! And that is the average pressure. And carbon dioxide is the principle gas in the atmosphere. Well, with 6 millibars, there's virtually no chance of having any liquid water.”
