Home Table of Contents What's New Image Index Copyright ScienceViews Search

On Mars: Exploration of the Red Planet. 1958-1978
 
 
ON THE SURFACE
 
 
 
[380] The first lander's first picture, of footpad 3 (a 60° high-resolution image), demonstrated to everyone that the craft was safely down on the surface. Minutes later, camera 2 began taking a real-time picture, a 300° panoramic view of the scene in front of the lander. These shots had been planned to provide the maximum amount of immediate information so that images of value would already have been collected should something unforeseen terminate the operation of the lander. Thomas A. Mutch, lander imaging team leader, recalled, "The planning for these first two frames was exhaustive.'' Characteristically, everyone had some advice about the best photographs to take. More than a year before the landing, team members had been called to Washington to brief NASA Administrator James Fletcher on camera strategy. "In the event of a botched landing, the first two images might constitute our only pictorial record of Mars." The pictures would be sent to the orbiter in the first 15 minutes after landing and thence to Earth. Not for 19 hours, including the first night on Mars, would it be possible to communicate again with the lander.
 
Some of Mutch's associates argued with the decision to photograph the footpad and then the view in front of the lander. One challenged, "If you were transported to an unknown terrain, would you first look down at your feet?" Mutch had to agree that the common mental image of the explorer was that of an individual shading his eyes with his hand looking far away to the horizon. He records that his counter argument was rather pedestrian. He thought-in the terms of a photogeologist-that the first picture of the footpad would he technically the better of the two:
 
A primary photogeologic goal, perhaps because it is so easily quantifiable, is increase in linear resolution. Looking straight down, the slant range was abut 2 m yielding a linear resolution of approximately 2 or 3 mm. Looking toward the horizon, nominally 3 km distant, the linear resolution would have been reduced toward two or three orders of magnitude.
 
Our logic would have been persuasive if the surface of Mars had been generally flat, but covered with small objects of unusual form. As it turned [381] out, this was not the case. The rock-littered surface in the near field is relatively undistinguished. But the undulating topography and diverse geology of the middle and far field is spectacular. From both an exploratory and scientific perspective, the panorama to the horizon is the more impressive of the first two pictures. 33
 
This self-effacing evaluation is characteristic of many of the Viking scientists, but especially of Tim Mutch. Seated in the "Blue Room" as the first electronic picture data began appearing on the television monitors throughout the Jet Propulsion Laboratory facilities, Mutch in almost a boyish manner commented, "The neat thing about pictures is that everyone can do their own analysis. We're really quite superfluous here." The images from the lander were reconstructed, picture element (pixel) by picture element from left to right, just as they had been taken by the camera on Mars. After going through the decoding process in the ground reconstruction laboratory, the image was shown throughout JPL a few lines at a time. From left to right, the first pictures of Mars began to evolve on the monitors. Reactions were varied, but nearly all were happy ones. For Tim Mutch, it was "a geologist's delight." Jim Martin saw the first picture in very practical terms-Viking was so far a success. He expressed his appreciation to the entire Viking team and to the "10,000 people across the country who deserve a part of the credit given to me." Mission Director Tom Young was also pleased with the performance of his spacecraft. As for the pictures, he said, "quality was consistent with what we should get, but they have exceeded my expectations." The quality was very good, and Young added that "Mars has demonstrated that it is photogenic!" 34
 
 
The Colors of Mars
 
 
The first two photos of Mars received on 20 July 1976 were followed by a color photograph on the 21st. A lot of people would not forget that first color picture. Mutch tells the tale as well as anyone. During the first day following the early morning lauding of Viking 1 , his team was preoccupied with analysis and release of those first two images, "which, in quality and content, had greatly exceeded our expectations." So much were they concentrating on the black and white pictures, that they were "dismally," to use Mutch's word, "unprepared to reconstruct and analyze the first color picture." Mutch and his colleagues on the imaging team had been working long hours, along with everyone else, during the search for a landing site. Despite enthusiasm, people were tired. Many of the Viking scientists in the upcoming weeks would have to learn to present instant interpretations of their data for the press. For the first color photograph, haste led to processing the Martian sky the wrong color.
 
In a general fashion, Mutch and his team understood that a thorough preflight calibration of the camera's sensitivity to the colors of the spectrum was necessary. They also knew that they would need computer software programs to transform the raw data efficiently into an accurate color....
 
 
[Whole page 382] 
 
 
The first photograph (above) from the surface of Mars, taken minutes after the Viking 1 lander touched down on 20 July 1976. Center of the image is about 1.4 meter from the lander's camera no.2. Both rocks and finely granulated material are visible. Many foreground rocks are flat with angular facets. Several larger rocks have irregular surfaces with pits, and the large rock at top left shows intersecting linear cracks. A vertical dark band extending from that rock toward the camera may have been caused by a one-minute partial obscuring of the landscape by clouds or dust. The large rock in the center is about 10 centimeters across. At right is a portion of the spacecraft's footpad, eith a little fine-grained sand or dust deposited in its center at landing.
 
 
 
 
Below is the first panoramic view by Viking 1 on the surface. Horizon features are about 3 km away. A collection of fine-grained material at left is reminiscent of sand dunes. Projections on or near the horizon may be rims of distant craters. Some of the rocks appear to be undercut on one side and partially buried by drifting sand on the other. The housing of the sampler arm, not yet deployed, and the low-gain antenna are at left. In the right foreground are the color charts for camera calibration, a mirror for the magnetic properties experiment, and part of a grid on top of the lander body. At upper right is the high-gain antenna for direct communication between the lander and Earth.
 
 
 
[383]....representation. "What we failed to appreciate were the many subtle problems which, uncorrected, could produce major changes in color. Furthermore, we had no intimation of the immediate and widespread public interest in the first color products-for example, intuitively corrected color images were shown on television within 30 minutes following receipt of the data on Earth." Although they resisted at first, the lander imaging team was obliged to release the first color prints within 8 hours of having received the image. 35
 
Instinctive reactions and intuition can lead to mistakes when dealing with an alien world. Here is Tim Mutch's first public reaction to the color photograph:
 
Look at that sky-light blue sky-reddish hue. It's a very exciting thing to see this distinct reddish coloration to the surface. These are subtle hues. It's a geological scene, a natural scene. Even in the deserts here on Earth the reds are not crayon reds as painted by a child. This is a surprisingly terrestrial-like desert scene. 36
 
But to borrow Carl Sagan's phrase, to see this picture in terms of deserts on our own planet was an "Earth chauvinism." The photo was of Mars, not of Earth; the sky should have been red. When James A. Pollack of the imaging team told a press conference on July 21 that the Martian sky was pink, he was greeted with some friendly boos and hisses. Sagan, in a way that only he could, chided the newspeople the following day: "The sort of boos given to Jerry Pollack's pronouncement about a pink sky reflects our wish for Mars to be just like the Earth." 37
 
There were three sensors with blue, green, and red filters in the focal plane of the camera to record the radiance of the scene in blue, green, and red light. The multilayer, interference filters used in the lander cameras (filters that could withstand the rigors of sterilization) have an irregular spectral response. The blue channel, for instance, responds slightly but significantly to light in the infrared portion of the spectrum. The unwanted part of the signal must be subtracted, "so that the absolute radiances at three specific wavelengths in the blue, green and red are represented." Subsequently, color prints were produced by exposing conventional color film to [384] individually modulated beams of blue, green, and red laser light, scanning the film with the same geometry employed in the camera.
 
Before the flight, the cameras had been calibrated and the sensitivity of each sensor-filter combination determined. "Qualitative tests indicated that simple normalization of the voltages for the three color channels was sufficient to produce reasonable color images. In making that judgment our attention was generally directed to saturated colors in the natural scene and test target." When the first color data were received, Mutch's specialists used the same normalization techniques to calibrate the image. "The result was surprising and disquieting. The entire scene, ground and atmosphere alike, was bathed in a reddish glow. Unwilling to commit ourselves publicly to this provocative display, we adjusted the parameters in the calibration program until the sky came out a neutral gray." The soil and rocks demonstrated good contrast, and the colors "seemed reasonable." This was the picture released eight hours later. "But in our chagrin," Mutch recalled, "the sky took on a bluish hue during reconstruction and photo-reproduction. The media representatives were delighted with the Earth-like colors of the scene."
 
While the television and newspaper reporters hurried to get this color print before their respective audiences, continued analysis supported the reality of an orangish tint throughout the scene. The atmospheric coloration was due to the presence of suspended soil particles in the thin air. Mutch recalled: "Several days after the first release, we distributed a second version, this time with the sky reddish. Predictably, newspaper headlines of Martian sky turns from blue to red were followed by accounts of scientific fallibility. We smiled painfully when reporters asked us if the sky would turn green in a subsequent version." Experience with color imaging over the next year indicated that the colors of Mars might vary, but the sky would retain its reddish hue. "In summary," Mutch said, "the color of the Martian scene, perceived by the necessarily abnormal eyes of Viking, is elusive. In response to the inevitable question: `Is that exactly how it would look if I were standing on Mars?' a qualified `yes' is in order." 38
 
 
A Real World
 
 
No matter what the color of the sky, the Viking pictures created a new reality for many people. Jerry Soffen said that, if any one thing stood out in his mind, "Mars had become a place. It went from a word, an abstract thought, to a real place." Soffen doubted that he would ever have an adventure like climbing Mount Everest, but he knew that it existed because other people had been there and had taken pictures of it, just as people had been to other extraordinary places on Earth. And now, their "guy" had made it to Mars. "He was not a person, but he was a close friend." For many associated with the Viking project, the lander had become personified. "It is like a person invented by a committee. And we sent him there and he did his thing....Before the Viking missions Mars was a fictional or fantasy....
 
 
[385] 
 
 
Two variations of the first color photo from the Viking 1 lander, taken on the Mars surface 21 July 1976. The blue-sky version above was released the same day. Below is the true red-sky version released 26 July. The red cast is probably due to scattering and reflection from sediment suspended int he lower atmosphere. To assist in balancing the colors, a photo was teaken of a test chart mounted on the rear of the spacecraft and the calibration then applied to the entire scene.
 

 
[386]
 
 
 
The two photographs above were taken with the Viking lander camera during tests in the summer of 1974. At the top is a panoramic shot from a site overlooking the Martin Marietta Corporation factory in Denver. The lower photo was taken at the Great Sand Dunes National Monument in southwestern Colorado. The lander camera is a facsimile camera, different in design from the television and film cameras which have been used on many space missions. The field of view is not imaged simultaneously. Instead, adjacent vertical lines are successfully scanned. Reflected light from each of the "picture elements" in the line is recorded on a very small photodiode in the focal plane of the camera. Twelve diodes are available for use, each optimized for a different distance and a different part of the visible near-infrared spectrum.
 
 
 
[387]
 
 

Photos permit comparison of the color of the Viking lander on Mars (at left) and Earth (above)- especially the orange cables. Tim Mutch used this guide to show that the red-sky rendition of the Mars landscape was the correct one. In the Earth photo, Jim Martin stands beside the science test lander in the Von Karman Auditorium at Jet Propulsion Laboratory.

 

 
[388]
 
 
Photos taken by the Viking lander camera provide comparison of an Earth scene (above) and one on Mars (below). In a photo taken near the Martin Marietta Denver facility during tests in 1974, tan and reddish sedimentary rocks have been tilted and eroded to form prominent cliffs. Data from three diodes (blue, green, and red) were combined for the color picture. Colors have not been balanced; the blue contribution is unnaturally large. For mission photos, colors were carefully calibrated. The Martian horizon stretches across nearly 200° in the composite of three color photos taken 4 September 1976 (center), 5 September (right), and 8 September (left). A thin coating of limonite (hydrated iron oxide) colors the surface predominantly rusty red, although some dark volcanic rocks can be seen. The horizon is flat because the photo has been rectified to remove the effects of the 8° tilt of the spacecraft.
 

 
 
[389]....place-the planet of Flash Gordon or some world peopled by Edgar Rice Burroughs. School children learn about the orderly progression of planets, and one of them has the same name as the world of many science fiction dramas. One Mars had physical, scientific properties like Earth; the other was a fantasy land. Now they could think of Mars as a genuine world. The shift from an object to be studied to a real place might not have been important scientifically, but it was a big change intellectually. 39
 
Soffen pointed out that his personal involvement with the planet seas not unlike that of the other Viking scientists. It had been eight years since the beginning of Viking. With the landing, the investigators were hungry for every bit of knowledge, any new speculation that would lead to a better understanding of the nature of Mars. Before the first photographs were received from the lander, Mars was more a scientific problem than an actual planet. When scientists talked about atmospheric conditions, they were describing numerical quantities that had an engineering significance for the designers. But it was difficult to think in terms of real clouds, real winds, real temperatures in the way we discuss our own weather. As the science fiction writers had built imaginary worlds on which their stories could take place, the scientists too had created a Mars that seemed to fit their assumptions. But the planet created from earlier known scientific facts had very little similarity to the Mars that the orbiter and lander cameras portrayed. Mars as a real place was much more complex and interesting than any that had been conjured up in the minds of scientists. The new Mars of Viking has as many complicated processes at work as does Earth.
 
Geologist Tim Mutch also had some personal reflections on what they had found awaiting them on Mars:
 
If you were to tell a geologist that you were going to go out to two places on Earth with your little Brownie to take one or two rolls of film at each locality and then were to come back and from this interpret the history of the planet, he would think you were out of your mind, the most absurd thing he had ever heard of. In a sense it is. So one should not overestimate the exclusive model that you can generate from pictures.
 
But one thing that could be said definitively was that the terrain of Mars was not bland. A complicated history is exposed particularly in the photographs taken at the Viking 1 site. "From a geological point of view, there is clearly a sequence of events represented....involving fundamentally different processes-for example, impact, wind, volcanic activity, possibly fluvial activity and possibly ground ice."
 
The specialists confirmed a diversity of rock types on Mars, indicating several petrographic types; that is, rocks that probably have different mineralogy and at least have different texture. More boulders seem to be on the surface than can be accounted for by impact processes; perhaps the weathering of bedrock or the deposition of rocks by fluvial mechanisms account for them. And the bedrock visible in the Viking images indicates that some [390] process, either fluvial or alluvial, is stripping off the soil to reveal the rock. At the Viking 2 site, the rocks are more homogeneous. "They are highly pitted, due to either volcanic vesiculation or to some peculiar process we simply do not understand," reported Mutch. Some scientists think Viking 2 landed on a wide-spread, fine-grain sediment mantle- the polar mantle. The boulders littering the scene were probably imposed, either as broken lava flows or as ejected boulders from a nearby crater. 40
 
Seeing another planet up close opened the way for comparison of two evolving worlds. With the passing of the romantic Mars and the gradual acceptance of the new Red Planet has come both excitement and disappointment. Looking at a tangible place is far more exciting than ruminations about abstract places, but the absence of life was a blow to many who had hoped to discover life or who had hoped that life might have had a chance to evolve. The biological and organic investigations indicated that the prerequisites for life on Mars were not evident at either landing site. 41