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Science: Mars: The Search Begins

14 minute read

As a Bicentennial spectacular, it was meant to be out of this world: a July 4 touchdown on Mars by Viking 1’s robot lander to begin the search for life on the red planet. But true to its name, Mars was being belligerent. The first landing site in the Chryse region appeared so hazardous on careful photographic analysis that Viking scientists concluded late last week that a birthday landing was out. That part of the American celebration would come somewhat later.

Even as the robot was sending data to its orbiting mother ship for relay back to scientists at the Jet Propulsion Laboratory in Pasadena, the other probe of the eight-year-old $1 billion Viking program was closing in on Mars. The twin Viking 2 spacecraft is scheduled to send still another lander to the Martian surface on Sept. 4, either to expand the search or to stand in for Viking 1 should something go amiss with the first lander. Scientists rate Viking’s chances of a successful landing at 70%. Unlike the Apollo lunar module, which could be maneuvered out of harm’s way by the astronaut pilot as it neared the moon’s surface, the unmanned Viking lander must descend along a preprogrammed path all the way to its touchdown. If it encounters a large boulder, a deep crevice, too steep a slope or high winds upon landing, the craft could topple over and be forever silenced. It might conceivably even sink, antennas and all, into soft ground or a deep layer of dust.

Ice Patches. Even if the Viking lander were equipped with television cameras that could spot a hazard as the surface loomed up, there would be nothing that J.P.L. controllers could do to evade the trouble. Viking’s picture signals, traveling at the speed of light, would not reach earth for 18 minutes, long after the little ship touched the surface. Signals from the controllers ordering Viking to avoid the site would take another 18 minutes to return to the craft, far too late to do any good. Russian space scientists can testify to the risks. In their four known attempts to land spacecraft on Mars, one ship missed the planet completely, two apparently crashed, and the fourth transmitted for only 20 seconds, sending an undecipherable portion of one picture before lapsing into silence.

Still, in the control center at J.P.L., there was confidence that Viking 1, despite the delay, would not fail. Other than a helium leak that caused excess pressure in the spacecraft’s propulsion system as it neared Mars, Viking had performed flawlessly since leaving Cape Canaveral last August on its journey across space. As it neared its destination a fortnight ago, gathering speed as the pull of Martian gravity increased, Viking took increasingly detailed pictures of Mars. They showed no evidence of the swirling sandstorms that had obscured the surface as Mariner 9 approached in 1971, and the proposed Viking landing site in Chryse was clearly visible. Even more significant to the scientists, the Martian atmosphere showed discernible traces of vapor—and bright patches of ice were visible in several craters. This seemed to be good evidence of the presence, in greater abundance than expected, of the substance essential to life as man knows it: water.

Melting Glacier. Last week, after Viking maneuvered into an elliptical orbit that carried it as low as 941 miles above the Chryse region once every Martian day (which is 24 hours, 37 minutes and 22.7 seconds long), the craft began taking detailed pictures of the landing site and its surroundings. As these shots—transmitted line by line —appeared on mission-control TV monitors, reports Geologist Harold Masursky, “people jumped up and down and hollered, shook hands and patted each other on the back. People kept saying ‘Wow!’ all night.” Apparently because the Martian atmosphere is clearer than it was at any time during Mariner 9’s nine-month photographic mission in 1971 and ’72, scientists could pick out even more details than were visible on the Mariner pictures. “I know how Lewis and Clark felt when they saw the West,” exulted Gerald Soffen, Viking’s chief project scientist. “It’s fantastic.”

The Viking photos reinforced the belief that water had once flowed on the surface of Mars. Project geologists were struck by the similarity of the Chryse landscape to the so-called “Spokane Flood”—the basalt highlands in the area where the Grand Coulee Dam straddles the Columbia River. Millions of years ago, water from a melting glacier carved and scarred these American highlands in a way that Masursky calls “almost an exact analogue to this Martian terrain.” On one ancient plateau in Chryse something, perhaps water, had etched out several layers of rock, cutting deep channels. Streamlined islands in some of the channels appeared to have been shaped by rushing water, which may also have produced extremely rough areas in parts of Chryse; rocks apparently torn loose by water litter the landscape. Other structures on the surface seem to be a part of an ancient, cratered terrain protruding through hardened lava on the surface of the plateau.

All in all, Chryse was considered more rugged than the scientists had been led to believe by Mariner 9 photographs and by radar profiling done so far with the huge radio telescopes at Goldstone, Calif., and Arecibo, Puerto Rico. While ruling out the initial Chryse landing site, Project Manager James Martin still hoped a second site in the Chryse basin might prove feasible. Even so, the change meant Viking 1 could not land on Mars at the earliest before July 8 —and perhaps not for weeks if both Chryse sites proved inhospitable, and it should be necessary to search out entirely new descent zones.

Dying Planet. Mankind’s preoccupation with Mars dates back to ancient societies, which considered the bright and red-hued planet to be a baleful influence. To the early Chinese, Mars was the planet of fire. Babylonians called it Nergal, after their god of death and pestilence, and the Greeks named it Ares, for their god of battle. Mars was also the Roman god of war. But it was not until the 17th century, when astronomers looked at the planet through the newly invented telescope, that Mars began to be widely regarded as another world. Astronomers Christiaan Huygens and Robert Hooke made sketches of Mars showing irregular markings, and Giovanni Cassini spotted the white polar caps. In 1784 Astronomer William Herschel suggested that the polar caps were ice and snow, noting that they expanded during Martian winters and shrank to their minimum size in late summer. He speculated that the planet had an atmosphere, clouds and life “in many respects similar to our own.”

In the 1870s Giovanni Schiaparelli, director of an observatory in Milan, drew detailed maps of Mars, giving distinctive markings (including Chryse) the classical names still used on Martian maps. He also recorded many canali (Italian for channels), which he noted have “led some to see in them the work of intelligent beings.” Soon an increasing number of astronomers were viewing and recording canals on Mars, none more energetically than Percival Lowell. At the observatory he founded in Flagstaff, Ariz., Lowell, beginning in 1894, meticulously drew maps showing elaborate networks of hundreds of Martian canals.

Lowell’s observations and writing struck an almost instinctive responsive chord in many people; they seemed to welcome the assurance that they were not alone, that life existed elsewhere in the universe. Fanciful tales about Martian life and travels flooded publishers’ offices. Among the more noteworthy were H.G. Wells’ 1898 novel War of the Worlds* and a series of Mars books by Edgar Rice Burroughs beginning with A Princess of Mars (1917). In fact, says Ray Bradbury, who himself has written some of the best contemporary science fiction about Mars, “Burroughs is more responsible for the space age than any scientist who ever lived, because Edgar Rice Burroughs with his imagination said to the ten-year-old boys of the world, ‘Stand on the lawn, put up your hand, go to Mars.’ ”

So strong was the belief in intelligent Martian life during this period that proposals were made to use the Siberian tundra as a blackboard for giant geometric figures that would show the Martians that earthlings were intelligent too. Others suggested digging trenches in the Sahara in the form of mathematical symbols, filling them with kerosene and water and setting them afire so Martians could see them at night. In 1920 Scientific American published proposals for signaling Mars with a system of searchlights and heliographs. Belief in Martian life persisted into the space age, despite measurements indicating only a tenuous atmosphere, scant traces of water, frigid temperatures and fierce solar ultraviolet bombardment of the planet’s surface.

Then came what should have been the greatest letdown for the true believers. In 1965 Mariner 4 passed within 6,118 miles of the Martian surface and returned pictures showing what seemed to be a lifeless, cratered, moonlike planet. But even those desolate scenes failed to dissuade the diehards. In 1965 Carl Sagan—then a relatively unknown Harvard astronomer, now the best-known proponent of Martian life and a member of the Viking-lander photoanalysis team—suggested that had a Martian version of Mariner 4 passed within 6,000 miles of earth and taken 22 comparable photographs, it would have uncovered no sign of life (TIME, Jan. 7, 1966). In fact, he noted, in studying hundreds of photographs taken by Nimbus and Tiros weather satellites orbiting only several hundred miles above the earth, he had failed to detect anything that could reasonably be interpreted as evidence of life below. The continuing confidence of Sagan and other life-on-Mars enthusiasts was bolstered in 1971 and ’72 when Mariner 9, from an orbit that brought it as close to the Martian surface as 825 miles, sent back thousands of pictures indicating that Mars was a dynamic, changing planet with violent weather, riverbeds and gulleys that appeared to have been carved out by running water.

Descent Path. So pervasive is the notion of life on Mars that even the most skeptical scientists at J.P.L.’s mission control last week could not help being caught up in the mounting excitement about the Viking landing. Said NASA Director James Fletcher: “Can you imagine the tension building as we wait for the first pictures from the Mars surface? What will we see? Those odd, vertical upthrusts of rock we’ve detected on radar maps, or something like an eye peering back at us? It’s all very exciting.”

That dramatic moment may be nigh.

If further studies of the second Chryse area satisfy scientists that it is safe for landing, controllers will feed the trajectory of the automated descent into the lander’s computers and give the craft a final checkout. Then, on instructions from the scientists, the lander, encased in a protective aeroshell, will be detached from the orbiter. About ten minutes later, two rocket engines in the aeroshell will begin firing, slowing the lander to bring it out of orbit and into a descent path. Some 150 miles from the surface, traveling at more than 10,000 m.p.h., Viking will encounter the outer fringes of the Martian atmosphere and be slowed by aerodynamic drag (the aeroshell will act as a shield to absorb frictional heat).

Martian Soil. At this point, instruments aboard Viking will begin sniffing the atmosphere, counting charged particles and identifying the gases as the craft descends. Farther down, other instruments will begin recording temperature, pressure and density of the thickening atmosphere. At 19,000 ft., now descending at only 560 m.p.h., the lander will unfurl a parachute, jettison its aeroshell and extend its landing legs.

Slowed to about 135 m.p.h. by the time it reaches 4,000 ft., Viking will begin firing its three descent engines, separate from its chute and approach the surface at less than 6 m.p.h. So that the landing site will be disturbed as little as possible, each of the braking rockets will fire through a showerhead arrangement of 18 nozzles to diffuse the blast. The rocket fuel is also hydrocarbon-free to avoid confusing Viking’s life-seeking instruments. When the first Viking foot pad touches Martian soil, it will trip a sensor that shuts off the engines. Eighteen minutes later controllers will know, by signals sent from the lander, if a successful touchdown has been made.

Viking will not wait for any congratulatory messages from Pasadena. Within seconds after touchdown, with almost unseemly haste, it will automatically point a camera down and take a picture of one of its foot pads and the surrounding soil. Scientists programmed this quick shot so that they could at the very least learn about grain sizes, erosion and other surface conditions near Viking’s feet in the event that some catastrophe befalls the craft soon after the landing. Six minutes later, like a wary human set down on alien soil, Viking will look cautiously up from its foot and shoot a panoramic view of its surroundings. An hour after landing, the first historic picture from the surface of Mars should be completed on J.P.L. monitors. It will be followed a half-hour later by the panoramic view, which if nothing else should help scientists to pinpoint the location of Viking, far too small to be seen by the orbiting mother ship.

Life Forms. It is possible — but not very likely — that these first pictures could dramatically show that there indeed is or was life on Mars. Shots of Fletcher’s “eye”— or a scraggly plant or an obvious fossil— would provide instant and sensational evidence that might forever change man’s view of himself, his world and the universe. In fact, Sagan and Stanford University Geneticist Joshua Lederberg have suggested that large organisms could have evolved in the cold and arid environment of Mars. Because a big animal has less surface area in relation to its volume than a smaller one, and because it is from an animal’s surface that heat and moisture are lost, explains Sagan, “organisms with an interest in the conservation of heat and water may select larger sizes.”The two scientists speculate that among the large life forms that could have evolved on Mars are “;petrophages” (rock eaters), which get their water and minerals from rocks; “crystophages” (ice eaters), which tap the permafrost beneath the surface; and creatures with shell-like shields for protection against the strong ultraviolet solar radiation that reaches the Martian surface.

If there is Martian life, in the view of most Viking scientists, it more likely exists in the form of tiny, hardy organisms too small for Viking’s cameras to perceive. It is these life forms that Viking’s ingenious biology laboratory is designed to seek out. Eight days after the landing—an interval during which Viking will monitor Martian weather and seismology and shoot the mission’s first color pictures—the ingeniously conceived and packaged laboratory (which occupies about a cubic foot of space) will begin operating. The surface sampler, a power-shovel-like bucket, will be extended from Viking by a boom that can reach 10 ft. It will scoop up a sample of Martian soil, which will then be distributed to three separate chambers of the laboratory. Using nutrients, radioactive tracers and analyzing devices, the lab will look for evidence of living organisms or their byproducts. Other experiments will identify both organic and inorganic substances in soil samples.

Sunlike Stars. Because of the complexity of the experiments and the time needed to interpret data at J.P.L., at least several weeks will pass before any definitive results of these life-seeking tests are known. If all of Viking 1’s tests —and those done later by Viking 2 —prove negative, the question of life on Mars will remain unresolved; the landers may simply be in the wrong places, or organisms may be thriving just a few inches below the deepest excavation of the sampler. Or Martian bugs may simply have chemistry so different from that of terrestrial life that Viking may be unable to recognize the alien processes.

If, on the other hand, a test proves positive—and is confirmed by repeated experiments—it might mark man’s most momentous discovery. For if any life, no matter how simple, has evolved on a planet so different from the earth, then it almost certainly must have arisen on countless planets orbiting sunlike stars in billions of galaxies throughout the universe. Man will know at last that he is not a cosmic freak, that he is not alone.

*Which in the form of a 1938 radio drama by a Welles named Orson was convincing enough to alarm and panic millions of Americans.

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